Swimming against the tide: Adrianus Pijper and the debate over bacterial flagella, 1946-1956

ISIS

Volumn 87, Issue 2, 1996, Pages 274-305

  Strick, James ^a  

^a PRINCETON UNIVERSITY   (United States)

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[No Author keywords available]

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EID: 0007526113     PISSN: 00211753     EISSN: 15456994     Source Type: Journal    
DOI: 10.1086/357484     Document Type: Article

References (155)

1. See, e.g., Albert Van Helden and Thomas L. Hankins, eds., Instruments, Osiris, N.S., 1994, 9.
2. In physics see, e.g., Brace Hevly, "Stanford's Supervoltage X-ray Tube," Instruments, Osiris, ibid., pp. 85-100;
3. Peter Galison, How Experiments End (Chicago: Univ. Chicago Press, 1987);
4. and John L. Heilbron, Electricity in the Seventeenth and Eighteenth Centuries: A Study of Early Modem Physics (Berkeley: Univ. California Press, 1990).
5. In biology see, e.g., Timothy Lenoir, "Helmholtz and the Materialities of Communication," Osiris, N.S., 1994, 9:185-207;
6. Robert G. Frank, Jr., "Instruments, Nerve Action, and the All-or-None Principle," Osiris, ibid., pp. 208-235;
7. Boelie Elzen, "Two Ultracentrifuges: A Comparative Study of the Social Construction of Artefacts," Social Studies of Science, 1986, 16:621-662;
8. and Hans-Jörg Rheinberger, "Experiment, Difference, and Writing, I: Tracing Protein Synthesis," Studies in History and Philosophy of Science, 1992, 25:305-331.
9. On the extensive discussion around Rockefeller Foundation support for importing expensive instruments into biology see, e.g., Pnina Abir-Am, "The Discourse of Physical Power and Biological Knowledge in the 1930s: A Reappraisal of the Rockefeller Foundation's 'Policy' in Molecular Biology," Soc. Stud. Sci., 1982, 12:341-382;
10. Evelyn Fox Keller, "Physics and the Emergence of Molecular Biology: A History of Cognitive and Political Synergy," Journal of the History of Biology, 1990, 23:389-409;
11. Robert E. Kohler, Partners in Science (Chicago: Univ. Chicago Press, 1991), pp. 265-406;
12. Lily Kay, "Laboratory Technology and Biological Knowledge: The Tiselius Electrophoresis Apparatus, 1930-1945," History and Philosophy of the Life Sciences, 1988, 10:51-72;
13. Kay, The Molecular Vision of Life (Oxford: Oxford Univ. Press, 1993);
14. Nicolas Rasmussen, "Making a Machine Instrumental: RCA, the Rockefeller Foundation, and the Beginnings of Biological Electron Microscopy in America," Stud. Hist. Phil. Sci., 1996, in press;
15. and Rasmussen, Picture Control: The Electron Microscope and Biology in America, 1940-1960 (Stanford, Calif.: Stanford Univ. Press, in press).
16. Adrianus Pijper, "Shape and Motility of Bacteria," Journal of Pathology and Bacteriology, 1946, 58:325-342.
17. On tensions between clinicians and bacteriologists see, e.g., Gerald L. Geison, "Divided We Stand: Physiologists and Clinicians in the American Context," in The Therapeutic Revolution: Essays in the Social History of American Medicine, ed. Morris J. Vogel and Charles E. Rosenberg (Philadelphia: Univ. Pennsylvania Press, 1979), pp. 67-90;
18. and Russell C. Maulitz, "Physician versus Bacteriologist: The Ideology of Science in Clinical Medicine," The Therapeutic Revolution: Essays in the Social History of American Medicine, ibid., pp. 91-107.
19. The categories commonly used were monotrichous (having a single flagellum at one pole), lopotrichous (having a tuft of flagella at one pole), amphitrichous (having flagella at both poles), and peritrichous (having flagella completely surrounding the cell). For an overview of opinions regarding flagella see A. L. Houwink and Woutera van Iterson, "Electron Microscopical Observations on Bacterial Cytology, II: A Study on Flagellation," Biochimica Biophysica Acta, 1950, 5:10-44, p. 11.
20. See J. H. Dible, Recent Advances in Bacteriology, 2nd ed. (Philadelphia: Blakiston, 1932), p. 84. Dible relates that the failure of Pijper and others to detect the antigens on the flagella that cause the clumping "is stated by these authors to be due to the use of formalinized or phenolized cultures, in which O agglutination is inhibited by the preservative" (p. 85). This early discovery may have been one source of Pijper's deep respect for the problem of artifacts, which would figure crucially in his later theory on flagella. Note that bacterial nomenclature was not highly standardized during this period, so that by the late 1930s and early 1940s Mudd and others in the United States referred to the typhoid organism as Eberthella typhosa, while Pijper and many Europeans called it Bacillus typhosus. By the late 1940s the name Salmonella typhosa was in widespread use, replacing most such older names. Most of the background available on Pijper comes from a few obituaries, e.g., in the
21. New York Times, 14 Jan. 1964, p. 31,
22. and from a brief description in A. F. Kamp et al., eds., Albert Jan Kluyver: His Life and Work (New York: Interscience, 1959), p. 9. Indeed, the scantiness of biographical information is testimony to the almost total submergence of his reputation. I wish to express my thanks to Pijper's daughter, Marie Hersch, who kindly sent me her collected "Adrianus Pijper Bibliography" and some additional obituaries. Pijper's student J. P. van der Walt has noted his talent as a clinician and diagnostician: "Pijper was at heart a microbe hunter, bent on tracking down the causative agents of unrecognized Southern African diseases." He also points to Pijper's extreme versatility in the lab: "It is currently almost impossible to appreciate the difficulties which the early bacteriologists had to contend with; Rickettsiae were not culturable on agar, and had to be recovered and maintained in vivo by injection into guinea pig testes (which were subsequently sectioned by microtome and then stained). Serology obviously played a central role. The three rickettsioses known in Southern Africa - louseborne typhus, rat-flea typhus, and tick-bite fever . . . , differ not only by their insect vectors, but also in their mutual immune response." J. P. van der Walt to James Strick, 24 May 1994; I appreciate this lively and detailed account.
23. Adrianus Pijper, "Begeisselung von Typhus- und Proteusbazillen," Zentralblatt für Bakteriologie, I. Abt. Orig., 1930, 115:113-121;
24. Pijper, "Nochmals über die Begeisselung von Typhus- und Proteusbazillen," Zentralblatt für Bakteriologie, I. Abt. Orig., ibid., 1931, 123:195-201;
25. Pijper, "Dark-ground Studies of Flagellar and Somatic Agglutination of B. typhosus" J. Pathol. Bacteriol., 1938, 47:1-17;
26. Pijper, "Microcinematography of the Motile Organs of Typhoid Bacilli," Journal of the Biological Photography Association, 1940, 8:158-164;
27. Pijper, "Dark-ground Studies of VI Agglutination of B. typhosus," J. Pathol. Bacteriol., 1941, 55:431-436;
28. and Pijper, "Micro-cinematography of the Agglutination of Typhoid Bacilli," Journal of Bacteriology, 1941, 42:395-409.
29. Stuart Mudd to Adrianus Pijper, 1 Dec. 1948, Stuart Mudd Collection in Medical Microbiology, UPC 2.9MM, Box 18, File P/1948-49, University of Pennsylvania Archives, Philadelphia (hereafter cited as Mudd Collection). For an approving early reference see Mudd to Robert D. Potter, 20 Sept. 1941, Box 14, unsorted, Mudd Collection. See also in this box an undated abstract of Pijper, "Dark-ground Studies of Flagellar and Somatic Agglutination," prepared by Mudd in 1940 or 1941. For citations of Pijper's work in contemporary reviews of bacterial cytology see, e.g., Rene J. Dubos, The Bacterial Cell (Cambridge, Mass.: Harvard Univ. Press, 1945);
30. I. M. Lewis, "The Cytology of Bacteria," Bacteriological Reviews, 1941, 5:181-230;
31. Georges Knaysi, Elements of Bacterial Cytology (Ithaca, N.Y.: Comstock, 1944), p. 95;
32. and Stuart Mudd and T. F. Anderson, "Pathogenic Bacteria, Rickettsias, and Viruses as Shown by the Electron Microscope," Journal of the American Medical Association, 1944, 126:561-571, 632-642.
33. H. E. Morton, "Proceedings of Local Branches," J. Bacteriol., 1943, 45:304-305. Morton kept copies of Pijper's films to loan out to microbiology instructors. These films are all still extant, and in remarkably good condition, at the American Society for Microbiology Archive, Albin O. Kuhn Library, University of Maryland, Baltimore County. My thanks to archivist Jeff Karr for help in finding and viewing them.
34. Adrianus Pijper, "Filming as a Method of Research in Microbiology," Antonie van Leeuwenhoek, 1947, 12:26-32, on p. 30;
35. Pijper, "Shape and Motility of Bacteria" (cit. n. 3);
36. and Pijper, "Dark-ground Studies of Flagellar and Somatic Agglutination" (cit. n. 6) (which described the technique in great detail).
37. Pijper, "Shape and Motility of Bacteria," p. 326.
38. One group of researchers had even created a new catch-all category for the most irregular types, in an apparent effort to save the existing category structure and the associated staining methods as tools for taxonomic purposes. Harold J. Conn and Robert Breed of the New York State Agricultural Experiment Station had tried to explain the observed variability as early as 1920 by proposing that all cells actually have several flagella (i.e., are peritrichous) but appear to have only one (i.e., to be monotrichous) in young preparations; see H. J. Conn and R. S. Breed, "A Suggestion as to the Flagellation of the Organisms Causing Legume Nodules," Science, 1920, 51:391-392.
39. This theory was still further generalized and the variable condition named "degenerate peritrichous" in Conn's lab almost twenty years later; see Conn and Gladys E. Wolfe, "The Flagellation of Bacteria," Science, ibid., 1938, 87:283-284.
40. This condition was claimed to be very common among soil bacteria and was used by the workers of this lab in arguing for a particular taxonomic scheme; see Conn, Wolfe, and Mark Ford, "Taxonomic Relationships of Alcaligenes Spp. to Certain Soil Saprophytes and Plant Parasites," J. Bacteriol., 1940, 39:207-226.
41. Pijper, "Shape and Motility of Bacteria," p. 327.
42. This process is similar to the H agglutination in S. typhosa, where immune globulins gradually stick to the flagellum, eventually forming a complete sheath around it, observed by Pijper in 1938 and 1.941. This was among the work of Pijper first noted by Mudd (see note 7, above) and confirmed by him with electron microscope studies; see Stuart Mudd and T. F. Anderson, "Demonstration by the Electron Microscope of the Combination of Antibodies with Flagellar and Somatic Antigens," Journal of Immunology, 1941, 42:251-266.
43. For the "braiding" explanation see, e.g., Franz Neumann, "Die Sichtbarmachung von Bakteriengeisseln am Lebenden Objekt in Dunkelfeld," Zentralbl. Bakteriol. 1. Abt. Orig., 1928, 109:143-178.
44. Mudd, Katherine Polevitzky, T. F. Anderson, and Georges Knaysi - all working with EM at the RCA Research Lab in Princeton, with the technical help of James Hillier - as well as R. C. Williams and Ralph Wyckoff of the National Institutes of Health labs in Bethesda, were all strongly predisposed to believe in the power of the electron microscope and the reality of the flagella shown by it. On their studies see, e.g., Stuart Mudd, Katherine Polevitzky, T. F. Anderson, and L. A. Chambers, "Bacterial Morphology as Shown by the Electron Microscope, II: The Bacterial Cell Wall in the Genus Bacillus," J. Bacteriol., 1941, 41:251-264;
45. Mudd and Anderson, "Selective 'Staining' for Electron Micrography," Journal of Experimental Medicine, 1942, 76:103-107;
46. Mudd and Anderson, "Pathogenic Bacteria, Rickettsias, and Viruses as Shown by the Electron Microscope," J. Amer. Med. Assoc., 1944, 126:561-571, 632-642; and
47. Knaysi, Elements of Bacterial Cytology, pp. 84-95. On their predisposition to believe in EM
48. see Rasmussen, "Making a Machine Instrumental" (cit. n. 2). Polevitzky had in fact come up with a theory that flagella were hollow tubes, using some very early micrographs from the fall of 1940, that she published in
49. "Pictures of Bacterial Forms Taken with the Electron Microscope," J. Bacteriol., 1941, 41:260. Mudd took a great interest in this theory; by 3 Dec. 1940 he had developed a set of calculations to back it up: Thomas Anderson Papers (unsorted), Box 1, "Bacterial Morphology II: Cell Membrane" File, American Philosophical Society Library, Philadelphia. In fact, by 22 May 1941 Mudd was enthusiastically expounding on "his" flagella theory in a conversation with Anderson: notebook entry, 26 June 1941, p. 54, Box 16, Anderson Papers. Interestingly, by Sept. 1941 Mudd had concluded that the theory was mistaken and was anxiously trying to suppress reports of it; see Mudd to Potter, 20 Sept. 1941 (cit. n. 7).
50. Pijper, "Shape and Motility of Bacteria" (cit. n. 3), p. 328.
51. In later papers Pijper became even more harshly critical of the electron microscopists' presumption that their interpretations would be accepted by others who hadn't even seen the photos. See Adrianus Pijper, "Bacterial Surface, Flagella, and Motility," Symposia of the Society for General Microbiology, 1949, 1:144-179, on pp. 150-151.
52. Pijper, "Shape and Motility of Bacteria," p. 328.
53. Pijper, "Bacterial Surface" (cit. n. 13), pp. 149-150, 148.
54. On the debates about artifacts in pictures of the bacterial nucleoid see Carl F. Robinow and Eduard Kellenberger, "The Bacterial Nucleoid Revisited," Microbiological Reviews, 1994, 58:211-232.
55. For accounts of controversies over other cell structures see, e.g., Hans-Jörg Rheinberger, "From Microsomes to Ribosomes: Strategies of Representation, 1930-1955," J. Hist. Biol., 1995, 25:49-89;
56. Nicolas Rasmussen, "Mitochondrial Structure and the Practice of Cell Biology in the 1950s," J. Hist. Biol., ibid., pp. 381-420;
57. and Rasmussen, Picture Control (cit. n. 2), esp. Ch. 2, on Mudd's work. On the active efforts of Mudd and his committee to establish the prestige of electron micrographs, as well as to establish and maintain hegemony over the authority to interpret them,
58. see Rasmussen, "Making a Machine Instrumental" (cit. n. 2).
59. A researcher whose investment in stains paralleled Mudd's in EM was H. J. Conn (see note 10, above), who had established a large part of his considerable reputation in microbiology as the chairman of the Commission on Biological Stains and the author of Biological Stains, which had run to five editions by 1946. Einar Leifson, beginning at Johns Hopkins in 1930, and later at Loyola University of Chicago, worked on developing specifically flagellar stains; for an early publication
60. see, e.g., Einar Leifson, "Development of Flagella on Germinating Spores," J. Bacteriol., 1931, 21:357-359.
61. Even after Pijper's 1946 publication, he continued to speak of flagellar staining as unproblematic, totally ignoring Pijper's challenge; see Leifson, "Staining, Shape, and Arrangement of Bacterial Flagella," J. Bacteriol., ibid., 1951, 62:377-389;
62. and Leifson, Atlas of Bacterial Flagellation (New York: Academic, 1960).
63. Pijper, "Shape and Motility of Bacteria" (cit. n. 3), p. 334.
64. Pijper, "Shape and Motility of Bacteria" (Ibid., p. 330. Pijper later elaborated his thinking along these lines: "From a general biological viewpoint the existence of dozens or more of holes in the cell wall . . . merely to let through a number of flagella, does not seem very acceptable. As Dubos (1945) has put it, flagella are not essential to the life of the cell. . . . It seems already very difficult to imagine how during normal movement actively motile flagella could pierce the cell wall from within, bend at right angles, run along the body of the bacterium, become twisted together into a tail and then unfold their propelling activity. What would happen to such structures during semi-somersaults and sudden reversals, or rather what they would have to do, and in complete unison, is quite beyond my imagination as to what is biologically and mechanically possible." Pijper, "Bacterial Surface" (cit. n. 13), pp. 156-157.
65. Pijper, "Shape and Motility of Bacteria," p. 331; and
66. Pijper, "Filming as a Method of Research" (cit. n. 9), pp. 30-31.
67. Pijper's project amounts to nothing short of an attempt to prevent the capture of the phenomena of bacterial motility by biochemistry and the nascent molecular biology, in order to retain them within the domain of microbiology. Indeed, Pijper delineated his view of this contest with a directness not usually seen in microbiology journals. He used the occasion of an issue of Antonie van Leeuwenhoek, the journal of the Netherlands Society of Microbiology, celebrating the work of the bacteriologist A. J. Kluyver to describe the current role of biochemistry relative to the older traditions of microscopy and morphology: "Microbiology can be approached in a variety of ways. . . . The present time witnesses an emphasis on biochemical approach, and this has enjoyed the consistent attention of Professor A. J. Kluyver and his school. . . . Bacterial taxonomy has never been quite satisfactory, witness the numerous 'systems' that have been advocated. By most workers morphology is still put first and foremost, and biochemistry or physiology second, whenever classifications of bacteria are discussed. There is no doubt however, that biochemistry is gaining ground, somewhat to the detriment of morphology. . . . The emphasis on biochemistry seems to me to be at least partly due to the idea that morphology is played out and has nothing further to offer. Microscopy of bacteria has gotten into a backseat. When it is still practiced, it uses staining processes with a distinct biochemical basis, it has become microchemistry. Considering all these matters from the viewpoint of a traditional medical bacteriologist, I have no fault to find. . . . But notwithstanding all this, I still believe that there is room for a purely morphological approach, based on the study of bacteria with a microscope. My contention however is that such studies should be undertaken on living material. I have a feeling that microbiology and especially bacteriology has rather neglected looking at bacteria in the live state. If I may bring up a parallel case, human pathology started in the post-mortem room. But the time is past that human pathologists are satisfied with the study of the dead body."
68. Pijper, "Filming as a Method of Research," pp. 26-27.
69. Pijper held up D'Arcy W. Thompson's book On Growth and Form (Cambridge: Cambridge Univ. Press, 1942) as a model of a productive morphological approach. He referred to this work repeatedly in his 1946 article "Shape and Motility of Bacteria."
70. Pijper, "Filming as a Method of Research," p. 32.
71. On Conn's reputation and role as a promoter and standardizer of biological staining see P. F. Clark, "A Half-Century of Presidential Addresses of the Society of American Bacteriologists," Bacteriol. Rev., 1953, 17:213-247, on p. 239; on the nickname "Dr. Stain" see Ware Cattell to H. J. Conn, 20 Dec. 1950, Harold Joel Conn Papers, Box 15, File Ca-Cn/1950-51, no. 22/2/661, Department of Manuscripts and University Archives, Kroch Library, Cornell University, Ithaca, New York (hereafter cited as Conn Papers). On Elrod see "Scientific Staff Biographies," Rockefeller University Record Group (RG) 450.1, Folder 2, Rockefeller Archive Center (RAC), Tarrytown, New York.
72. H. J. Conn and R. P. Elrod, "Concerning Flagellation and Motility," J. Bacteriol., 1947, 54:681-687, on p. 686;
73. and R. P. Elrod to Conn, 19 June 1947, Box 11, File Elrod, Conn Papers. See also James Strick and Nicolas Rasmussen, interview with James Hillier, 4 Dec. 1992. Contact with Hillier had been established through Alvin Hofer of Conn's lab (see Alvin Hofer, "Electron Microscopic Studies on Azotobacter Flagellation and Rhizobium Bacteriophage," J. Bacteriol., 1944, 47:415-416) and by Elrod at the Rockefeller labs in Princeton - from which many, including Wendell Stanley, made the short stroll to Hillier's lab to use the RCA microscope.
74. H. E. Morton to Conn, 9 Feb. 1948, Conn to Morton, 11 Feb. 1948, Box 14, File Mo-Mz/1948-49, Conn Papers. Conn and Elrod received congratulations from Henry Koffler at Purdue, who said that his recently begun studies on flagella were strongly influenced by the paper. Roger Stanier at Berkeley was also laudatory and asked if prints of some of the better electron micrographs could be made available for a text he was about to begin in collaboration with Michael Doudoroff. Conn and Elrod were elated; moreover, collaboration with someone of Conn's stature may have helped Elrod land his new job as chair of bacteriology at the University of South Dakota, Vermillion. See Henry Koffler to Conn, 16 Jan. 1948, Box 14, File K/1948-49; Roger Stanier to Conn, 14 Jan. 1948, Box 14, File Sn-Sth/1948-49; and Conn to Elrod, 21 Jan. 1948, Box 13, File E/1948-49, Conn Papers. Koffler was particularly thrilled when Conn lent him an electron micrograph by Woutera van Iterson, discussed later in this essay (cover illustration). He wrote back: "The shot is absolutely breath-taking and gives us something to aim at in our work. . . . I wanted to have as many of my colleagues as possible" see it; see Koffler to Conn, 9 Feb. 1948, Box 14, File K/1948-49, Conn Papers.
75. D. T. Smith et al., Zinsser's Textbook of Bacteriology, 9th ed. (New York: Appleton-Century-Crofts, 1948), pp. 22-27, on p. 27:
76. "Electron micrographs of Treponema pallidum . . . by Mudd, Polevitzky and Anderson (1943) revealed flagella. . . . Our own observations, with the darkfield apparatus, of various types of spirochetes . . . convince us that spirochetes move by contraction of their protoplasmic bodies and not by flagella. . . . Direct observation in the hanging drop or in the darkfield is a much more reliable method for detecting motility than the staining of flagella." See also Rene Dubos, Bacterial and Mycotic Infections of Man (Philadelphia: Lippincott, 1948), pp. 21-22.
77. Frank Johnson and R. F. Baker, "The Electron and Light Microscopy of Beggiatoa," Journal of Cellular and Comparative Physiology, 1947, 30:131-140, on p. 133.
78. Johnson qualified his support only by saying that observations he had made on flagella of the organism Spirillum volutans suggested that it was an exception, having flagella genuinely involved in motility in propeller-like fashion, so that Pijper's claim was "possibly not of universal application among bacteria." Johnson had previous experience with EM of flagella, for he had used the demonstration model up the road at RCA, at first with the assistance of Nina Zworykin, to investigate the cytology of luminous bacteria. See Johnson, "A Biologist's Letter to Three Daughters," unpublished manuscript. My thanks to Mary Johnson for allowing me access to her late husband's papers. For a report on the colloquium see Department of Biology Historical Subject Files, Princeton University Archives, Seeley Mudd Library, Princeton, New Jersey. Johnson made a habit of defending iconoclastic theories, according to his colleague John Tyler Bonner (conversation with James Strick). One result of the Princeton colloquium was a supportive comment on Pijper's theory in Bonner's influential 1952 book Morphogenesis (paperback ed., New York: Atheneum, 1963), pp. 152-153.
79. Woutera van Iterson, "Some Electron-Microscopical Observations on Bacterial Cytology," Biochim. Biophys. Acta, 1947, 1:527-548;
80. and Woutera van Iterson to James Strick, 9 Dec. 1992. Van Iterson was the daughter of the managing director of the Netherlands State Mines and a niece of the former director of the Botany Laboratory at the Technische Hogeschool who had hired Kluyver. She was a very enthusiastic proponent of EM - so much so that she personally persuaded Anton Philips, head of the giant Dutch electronics firm, of the importance of developing the electron microscope commercially. See J. B. LePoole, "Early Electron Microscopy in the Netherlands," in The Beginnings of Electron Microscopy, ed. P. W. Hawkes (New York: Academic, 1985), pp. 387-416, on p. 405.
81. On the new technique see R. C. Williams and R. W. G. Wyckoff, "Applications of Metallic Shadow-casting to Microscopy," Journal of Applied Physics, 1946, 17:23-33.
82. This technique is, however, one of those specifically cited in 1951 by Knaysi as having proved disappointingly limited in their ability to resolve questions about flagella; see Georges Knaysi, Elements of Bacterial Cytology, 2nd ed. (Ithaca, N.Y.: Comstock, 1951).
83. Elrod to Conn, 27 June 1947, 2 July 1947, and Conn to Elrod, 30 June 1947, Box 11. File Elrod, Conn Papers. Kluyver had originally sent the photo to Wendell Stanley at Rockefeller, as a memento of Stanley's recent visit to Delft. Elrod borrowed it and immediately wrote to ask Kluyver for permission to use it in "Concerning Flagellation and Motility"; he then wrote to Conn, so enthused that he speculated as to whether they might be able to use it even without Kluyver's permission. In the event, Kluyver denied permission because van Iterson's paper had not yet appeared in print, and Conn and Elrod had to content themselves with describing the photo and extolling its conclusiveness against Pijper. A few months later Conn wrote Kluyver: "You wish there were some favor you might grant me. . . . Indirectly your lab did me a distinct favor last year. I refer to your sending Dr. Elrod a copy of Miss van Iterson's beautiful electron micrograph. . . . This is referred to in our recent paper . . . and helped us very much in forming the concept expressed in that paper": Conn to A. J. Kluyver, 5 Feb. 1948, Box 14, File K/1948-49, Conn Papers. See also note 22, above, and the cover illustration.
84. Elrod to Conn, 27 June 1947: "It [the photo] proves without reasonable doubt the attachment of flagellum and bacterial cell. . . . This flagellum which is so regular in its entire aspect cannot be conceived as an artifact. . . . I might also add that the apparent striations of the flagellum indicate that it is protein in nature, not polysaccharide." This last conclusion he was to take back in his letter of 2 July, since "I was somewhat hasty in ascribing a proteinaceous substrate to striated structures. I find that a high intensity microscope can produce these artifacts. . . . Nevertheless, the protein nature of the flagella is more than a good possibility." I include these excerpts because they reflect the enthusiastic confidence of an early user of EM in what the photos can be relied on to show - a confidence not much shaken by the discovery that some of the visually compelling features were in fact artifacts.
85. "Flagella, if present, arise from the protoplast and pass through the cell wall, at least in vibrios. They are of uniform diameter somewhat characteristic of the bacterial species. They are not artefacts or mucous threads": Stuart Mudd, "Submicroscopic Structure of the Bacterial Cell, as Shown by the Electron Microscope," Nature [London], 1948, 161:302-303, on p. 302. Mudd made a more sweeping statement at the symposium but was advised by Knaysi and Hillier to qualify it as established with certainty only for vibrios, as well as to add "somewhat" before his more sweeping "characteristic of the bacterial species." He would not include, after the vibrio qualification, the further sentence they suggested: "In other groups of bacteria, however, their origin has not yet been clearly observed." See James Hillier and Georges Knaysi to Mudd, 2 Sept. 1947, Box 17, File H/ 1947-48, Mudd Collection.
86. Van Iterson had won a National Institutes of Health junior research fellowship to spend Sept. 1947-June 1948 working in Wyckoffs lab in Bethesda and Francis Schmitt's lab at MIT to broaden her experience with EM. See Hillier and Knaysi to Mudd, 2 Sept. 1947, Hillier to Mudd, 15 Apr. 1948, Box 17, File H/1947-48; van Iterson to Mudd, 14 Jan. 1948, Box 17, File V/1947-48; and Mudd to C. F. Robinow, 22 Nov. 1948, Box 18, File Robinow/1948-49, Mudd Collection.
87. Mudd to B. C. Brunstetter, 9 Nov. 1948, Box 18, File V/1948-49 (quotation); and Mudd to William Burrows, 27 Oct. 1948, Box 17, File B/1948-49, Mudd Collection. For the textbook see William Burrows et al., Textbook of Bacteriology, 15th ed. (Philadelphia: Saunders, 1949). Conn had just retired (though, as we have seen, he was still active behind the scenes in lobbying against Pijper), and Mudd may have felt that he was the only voice actively publishing in opposition to Pijper's considerable reputation and already numerous publications promoting his new theory.
88. Mudd and Millier had both thought that making flagella visible as motor organs was one of their first practical triumphs with the early RCA model B. And when Mudd's first theory of flagellar function did not pan out, his effort to prevent the science editor of the American Weekly from including it in a 1941 story about the RCA microscope illustrates well Mudd's attempt to keep the electron microscope associated only with success: "We are completely at a loss to know whether the earlier pictures were in error or whether we have been unable to get the conditions repeated again. At all events, it would be terribly embarrassing and unfortunate to have this hypothesis further elaborated until we know whether it has any basis in fact or not. . . . Changes have been indicated in your article to take care of all these points." See Rasmussen, "Making a Machine Instrumental" (cit. n. 2); Rasmussen, interview with Hillier, 12 Feb. 1992; and Mudd to Potter, 20 Sept. 1941 (cit. n. 7). See also note 12, above, on Mudd's early theories on flagella. By the summer of 1951 Mudd was already casting van Iterson's work of the summer of 1948 as seminal: "I shall be looking forward to some more contributions as significant as your now classic work on flagella." Mudd to van Iterson, 17 July 1951, Box 21, File V/1951-52, Mudd Collection.
89. Pijper to Mudd, 16 Sept. 1948, Box 18, File P/1948-49, Mudd Collection (Nature article, "aware of my existence");
90. and Adrianus Pijper, "Evidence that Amputation of Bacterial Flagella Does Not Affect Motility," Science, 1949, 109:379-380, on p. 380. He also lamented that a new text by Tanner and Tanner referred obliquely to his view without citing him and then went on to say that flagella are real motor organs, even if some cells appear to have motility without them. Mudd's electron micrographs illustrate their discussion, but this fatherson team used none of Pijper's famed dark-field photos.
91. See F. W. Tanner and F. W. Tanner, Jr., Bacteriology, 4th ed. (New York: Wiley, 1948).
92. Their discussion on flagella is on pp. 84-86, with Mudd's pictures as figures 29, 33, 34, and 47. The article mentioned in the last quotation appeared as Adrianus Pijper, "The Flagella of Spirillum volutans," J. Bacteriol., 1949, 57:111-118.
93. Millier to Pijper, 15 Oct. 1948, Box 18, File H/1948-49, Mudd Collection. Even later, in 1951, Knaysi was also willing to state that "it was once thought that this question [of flagellar attachment] could be easily settled by the electron microscope. This, however, proved to be a false hope": Knaysi, Elements of Bacterial Cytology, 2nd ed. (cit. n. 26), p. 213.
94. For Hillier's insistence on the superiority of EM in comparison to dark-field observation see, e.g., Hillier to Knaysi, 14 Jan. 1952, Box 20, File H/1951-52, Mudd Collection. Knaysi had broken ranks with Mudd and Hillier, challenging their claim of "bacterial mitochondria" in a letter to Hillier dated 6 Dec. 1951, and Hillier was chastising, trying to bring him back into line: "for this reason I do not consider the optical micrographs that you sent as being really good evidence that mitochondria do not exist. Unfortunately, at this level the resolving limit of the light microscope presents a very important difficulty. . . . This is precisely the basic error that Pijper has been making in his flagella studies. I would not like to see the same error creep into our thinking." On the rediscovery of Pijper's technique and rejection of Hillier's argument see R. M. Macnab, "Examination of Bacterial Flagellation by Dark-field Microscopy," Journal of Clinical Microbiology, 1976, 4:258-265, esp. p. 258, regarding a closely related argument: "It is commonly stated in microbiological texts that because bacterial flagella have a diameter (typically 15 nm) that is small . . . they cannot be seen by light microscopy. Such statements are erroneous and are based on a misconception of the limit set by the wavelength of light. This limit is one of resolution, not of detection." Macnab was not aware of Pijper's work before rediscovering dark-field observation of flagella; he used brilliant halogen lighting rather than sunlight. However, when he later read Pijper's articles from the 1940s he concluded immediately that Pijper had seen in every detail what he reported observing: R. M. Macnab to Strick, 7 Jan. 1993. Interestingly, despite the public insistence after ca. 1948 by Hillier, Mudd, van Iterson, and others on the undeniable superiority and lack of ambiguity of electron microscopic photos of flagella, debate and doubt about the meaning of some structures did continue within the privacy of the electron microscopic community. Mudd, for instance, wrote to Wyckoff only a year later, pointing out that certain "whisker-like processes" outside cells of pneumococci were probably in reality artifacts, some kind of precipitate. Wyckoff agreed, adding "and I am sure that the same thing goes for other delicate processes we see around bacterial cells. Evidently it is going to be difficult to decide in many cases when we are dealing with true flagella": Ralph Wyckoff to Mudd, 21 Oct. 1949, Box 18, File W/1949-50, Mudd Collection (Wyckoffs letter quotes Mudd).
95. Pijper to Hillier, 15 Nov. 1948, Box 18, File H/1948-49, Mudd Collection. Pijper repeated his arguments about the mechanical impossibility arid biological improbability of separate fibers perforating the cell wall and then executing maneuvers that a circus acrobat would envy. Next he addressed the pictures, "which are supposed to show that, what you call flagella, originate from small spherical bodies. This is to my mind not at all obvious because there are several small spherical bodies quite unattached to any fiagellum and there are similar bodies dispersed all over the field." He also saw no basis for the claimed ability to distinguish flagella supposedly lying below the cell from those lying above it in these photos.
96. Ibid. A new type of artifact had just been discovered, Pijper claimed, once again because of his insistence on working with living material. In studying the flagella of Spirillum volutans, he noticed that as the organisms died, the protoplast shrank back from the cell wall and the wall developed spots that blew out in bubble-like bulges. Pijper claimed that the bursting or collapsing of these bubbles during preparation of the specimen for EM could be responsible for some of the features seen in Hillier's micrographs that appear as regular circular perforations of the wall. In "Flagella of Spirillum volutans" (cit. n. 33) he described in detail how the features of a much-cited photo of Spirillum serpens by van Iterson (see Figure 6) could be explained as totally artifactual because of this phenomenon, combined with a rotation of the cells during drying and strands coming to rest either on top of or underneath the cell (see Figure 7). Pijper also addressed van Iterson's photograph of V. metchnikovii. His main claim in this paper was that he had discovered that the flagella of spirilla were very different from those of Salmonella typhosa and similar motile bacteria and were in fact fairly rigid and fixed in their point of attachment. In looking at van Iterson's 1947 paper and photos, he concluded that vibrios appeared to be similar to the large spirilla, so that "the flagellum is (in both) . . . a continuation of the cell wall, and not, as in most motile bacteria, mucous twirls derived from the capsule. And so my views on the nature and attachment of these structures in motile bacteria cannot be affected by observations in either vibrios or large spirilla": ibid., pp. 116-117. His opponents could not label this as pure sophistry, defining categories to include anything not fitting the theory, since it was based on actual observed differences with equipment that none of them could as yet duplicate.
97. Pijper, "Amputation of Bacterial Flagella" (cit. n. 33), p. 379.
98. Mudd to Pijper, 1 Dec. 1948, Box 18, File P/1948-49, Mudd Collection.
99. Pijper to Mudd, 15 Dec. 1948, Box 18, File P/1948-49, Mudd Collection. On the state of South African science at this time, Sydney Brenner remarked: "It was a very underdeveloped country, scientifically - a provincial country. . . . Facilities for research were quite - primitive. I mean, if you wanted to stain something, you first synthesized the dye." See Horace Freeland Judson, The Eighth Day of Creation (New York: Simon & Schuster, 1979), pp. 230-231.
100. For more detailed analysis of epistemological debates over what is fact and what artifact in electron microscope photos see Nicolas Rasmussen, "Facts, Artifacts, and Mesosomes: Practicing Epistemology with the Electron Microscope," Stud. Hist. Phil. Sci., 1993, 24:227-265; and Rasmussen, "Mitochondrial Structure and the Practice of Cell Biology" (cit. n. 16). In the debate between George Palade and Fritiof Sjöstrand, a basic disagreement over criteria paralleled Pijper's exchanges with his critics quite closely. Given choices of numerous different fixing and staining procedures, which resulted in different appearances of the same specimens, electron microscopists disputed at length over which procedures were most likely to produce true "lifelike" appearances in their micrographs. This included disputing criteria for what kind of appearance was likely to represent a true living structure.
101. In one exchange with Claes Weibull, for instance, Pijper emphasizes that his conclusions are based on a huge number of hours of observations on live bacteria over a period of twenty years, insisting that this surely has to count for something compared to Weibull's few years of biochemical analysis on flagella separated from destroyed cells, with no observations on actual moving bacteria. See Adrianus Pijper, "Bacterial Flagella," Nature, 1951, 168:749-150,
102. on p. 750. In his last word on flagella before his death in 1964, Pijper took Leifson (see note 16, above) to task in a similar vein: "Also, for proper measurements . . . it is essential to use 'fair samples' without selection, and to use large numbers. These conditions can only be fulfilled by using photomicrographs of flagella on live bacteria . . . where hundreds of wavelengths without any need for 'skipping' were available for measurement. . . . These measurements proved with mathematical exactitude that individual species of bacteria have specific wavelengths." Adrianus Pijper, "A New Heliostat for Dark-Ground Microscopy," Journal of the Royal Microscopical Society, 1962, 81:61-66, on p. 62.
103. Thus, in response to experiments where the flagella were stuck to the slide by antibiotic treatment and the cell bodies appeared to continue rotating around the stuck flagellum, Pijper reported: "I have repeated these experiments and made a film of them and find them inconclusive. I think these grotesque movements are more readily explained by bodily contortions." Pijper, "Bacterial Flagella," p. 750.
104. In a letter to van Iterson dated 10 Feb. 1949, Mudd suggests a hypothesis that is "pure speculation" but possibly "a useful stimulus" about the "basal granules" in the micrographs she had taken and how they might function in imparting motion to the flagella. In its purely speculative tone it is reminiscent of "his" theory (usurped from Polevitzky) of 1940-1941. He puts it to van Iterson almost sheepishly, saying he knows her to be characterologically averse to such speculation. She replied, "You are right with my character. I am not in favor of adding to a 'morphology' paper a pure hypothesis on 'function' by lack of any experiments on 'function.' I leave this gladly to our friend Pijper": van Iterson to Mudd, 20 Feb. 1949, Box 18, File V/1948-49, Mudd Collection. Mudd had suggested in his letter that perhaps van Iterson could visit Pijper's lab and observe his technique at first hand, to try to establish some common ground. Pijper seemed mildly interested, though he suggested she might not find to her liking the level of facilities and conditions in general, again lamenting "the complete lack of scientific interest and support from the authorities that govern this institute." By this time both Mudd and Hillier had concluded, however, that Pijper had gotten himself so far out on a limb that "it is quite hopeless to expect him to recede from his position at all." Hillier thought that Pijper was "in such a state of mind . . . that nothing in the world will ever convince him of his error." Mudd observed: "Other people, I hope, . . . will be more accessible to the implications of new evidence." In response to Pijper's claim that the spirilla studies were new evidence, Mudd could only ask: "Is it not amazing what an idee fixe can do to a man's common sense and scientific judgment?" Pijper to Mudd, 15 Dec. 1948 (cit. n. 40); and Hillier to Mudd, 30 Dec. 1948, Box 18, File H/1948-49; Mudd to van Iterson, 25 Jan. 1949, 10 Mar. 1949, Box 18, File V/1948-49, Mudd Collection.
105. Mudd to van Iterson, 25 Jan. 1949, 21 Mar. 1949, Box 18, File V/1948-49, Mudd Collection. See T. Y. Kingma Boltjes, "Function and Arrangement of Bacterial Flagella," J. Pathol. Bacteriol., 1948, 60:215-287;
106. and Kingma Boltjes, "Comment on Pijper's Film of Moving Bacteria," Ant. van Leeuw., 1948, 14:251-255.
107. The article Mudd referred to in his second letter was W. T. Astbury and Claes Weibull, "Xray Diffraction Study of the Structure of Bacterial Flagella," Nature, 1949, 163:280-282.
108. Warren Weaver to Gerard Pomerat, 25 Mar. 1949, Box 8, Folder 81, Series 800D, RG 1.1, Rockefeller Foundation Archives, RAC. See W. T. Astbury, "Flagella," Scientific American, Jan. 1951, 184:21-24;
109. The Svedberg and Arne Tiselius, "Report on Research Work in the Institute of Physical Chemistry, Sept. 1945-Sept. 1946," p. 2; "Report on Research Work . . . Oct. 1946-Dec. 1947," p. 2; and "Report on Research Work . . . 1 Jan.-31 Dec. 1948," p. 2, Box 8, Folder 81, Series 800D, RG 1.1, Rockefeller Foundation Archives. On Tiselius, the "protein network," and the "Uppsala-Rockefeller axis" see Lily Kay, "The Intellectual Politics of Laboratory Technology: The Protein Network and the Tiselius Apparatus," in Center on the Periphery, ed. Svante Lindqvist (Canton, Mass.: Science History Publishers, 1993), pp. 398-423.
110. Arne Tiselius to the Rockefeller Foundation, 15 June 1949, p. 2, Weaver to Tiselius, 9 Dec. 1949, Box 8, Folder 82; and "Report on Research Work in the Institute for Physical Chemistry, the Institute of Biochemistry, and the Gustaf Werner Institute for Nuclear Chemistry, Univ. of Uppsala, Jan. 1-Dec. 31, 1949," p. 6, Box 8, Folder 83, Series 800D, RG 1.1, Rockefeller Foundation Archives. On the fibers as comparable to other proteins see "Report on Research Work . . . Jan. 1, 1950-June 30, 1951," p. 7, Folder 83, Box 8, Series 800D, RG 1.1, Rockefeller Foundation Archives; Astbury, "Flagella"; and W. T. Astbury, "Hairs, Muscles, and Bacterial Flagella," Royal Institution of Great Britain, Meetings,
111. Weekly Evening Meeting, 4 May 1951. See also Claes Weibull, "Some Chemical and Physico-chemical Properties of the Flagella of Proteus vulgaris," Biochim. Biophys. Acta, 1948, 2:351-361;
112. Weibull, "Morphological Studies on Salt-Precipitated Bacterial Flagella," Arkiv for Kemi, 1949, 1:21-23;
113. Weibull, "Movement of Bacterial Flagella," Nature, 1951, 167:511-512;
114. and Weibull, "Reply to Pijper," Nature, ibid., 168:150.
115. Warren Weaver, 3 Dec. 1948, "Report on NS," pp. 3, 22, Box 2, Folder 14, Series 915, RG 3.1, Rockefeller Foundation Archives. Pijper's outreach to Astbury is exemplified by his use of a quotation from Astbury as the epigraph to his 1946 article "Shape and Motility of Bacteria" (cit. n. 3). On Astbury as a valued client of Weaver's see Pnina Abir-Am, "Discourse of Physical Power and Biological Knowledge" (cit. n. 2); on Weaver's project overall see Kohler, Partners in Science (cit. n. 2), pp. 265-406.
116. Van Iterson to Mudd, 20 Feb. 1949 (cit. n. 43). The "tje" ending is a Dutch diminutive.
117. Ibid.
118. T. F. Anderson, "Report on Visit to England and France, April 1949," pp. 5, 6, Box 12, Anderson Papers (cit. n. 12).
119. N. W. Pirie, "Structure and Activities of the Bacterial Surface," Nature, 1949, 163:897-898;
120. see also his introduction to the conference proceedings, in Symposia of the Society for General Microbiology (cit. n. 13), pp. 1-8, and his comments on the discussion of Pijper's paper in the volume, pp. 160-177 of "Bacterial Surface, Flagella, and Motility" (cit. n. 13), on p. 176. Pirie, a society official, chaired the conference.
121. Kluyver's concerns about Pijper are reported in Breed to Conn et al., 20 Jan. 1949, Box 13, File Breed/ 1948-49, Conn Papers. In one of a series of regular confidential check-in letters with his staff, Breed said: "I want a report from Parker on their recent symposium led by Stuart Mudd, taking Pijper's curious ideas regarding flagella to pieces. Did I tell you that although Pijper is a highly regarded brother-in-law of Dr. Kluyver, he (K.) was wondering how he could publish his own criticisms of these theories . . . when I talked with him in Copenhagen. He did it later in Antonie van Leeuwenhoek through a student [Kingma Boltjes]." Van Iterson reports Kluyver's growing distress, adding that "when I returned from the London meeting, I expected to find Pijper in the lab with Kluyver," but to her surprise he was not. "This made the whole affair the more tragic": van Iterson to Strick, 10 July 1995. Bert Theunissen has recently suggested that Kluyver and Gerrit van Iterson (VVoutera's uncle) were interested in dismissing and playing down the emphasis on variability among microbes on the part of Martinus Beijerinck in their construction of a founding myth about the Delft School of microbiology around 1940; see Theunissen, "The Beginnings of the 'Delft Tradition' Revisited," paper presented at the History of Science Society annual meeting, New Orleans, Oct. 1994.
122. For the treatment of Pijper in the new textbook see D. Smith et al., Zinsser's Textbook of Bacteriology, 10th ed. (New York: Appleton-Century-Crofts, 1952), p. 27. Elrod, van Iterson, Kingma Boltjes, and Weibull all got a considerable career boost from "successfully disproving" the views of an established figure, especially with the help of Conn, Mudd, William Astbury, Arne Tiselius, and others in casting flagella as an important subject for the nascent molecular biology.
123. James Millier, "Electron Microscopy of Microorganisms and Viruses," Annual Review of Microbiology, 1950, 4:1-20, on p. 9.
124. Adrianus Pijper, "Bacteriological Nomenclature," Lancet. 1948, no. 2, p. 196;
125. "Septem contra Pijper," Lancet. ibid., 1952, no. 1, pp. 88-89;
126. and "More Heresy," Lancet. ibid., no. 2, p. 769.
127. Pijper's New York Times obituary is cited in note 5, above. For some of his early publications in the
128. Lancet
129. see, e.g., Lancet1924, no. 2, pp. 367-368;
130. Lancet1926, no. 1, pp. 88-89;
131. Lancet1929, no. 1, pp. 182-183;
132. Lancet1931, no. 2, pp. 1183-1185;
133. Lancet1935, no. 1, pp. 1152-1154. For major reviews claiming that Pijper's work had been disproven
134. see Woutera van Iterson, "Some Remarks on the Present State of Our Knowledge of Bacterial Flagellation," International Congress of Microbiology, Symposium on Bacterial Cytology (1953), pp. 24-38
135. (Mudd was the U.S. chair in charge of organizing this symposium and arranged for van Iterson to be the speaker on flagella); Kenneth Thimann, The Life of Bacteria (New York: Macmillan, 1955), pp. 52-57;
136. Johannes Kvittingen, "Some Observations on the Nature and Significance of Bacterial Flagella," Acta Pathologica et Microbiologica Scandinavica, 1955, 37:89-93;
137. and B. A. D. Stocker, "Bacterial Flagella: Morphology, Constitution, and Inheritance," Symp. Soc. Gen. Microbiol., 1956, 6:19-40.
138. Later Pijper articles include (in chronological order - and, after 1956, in steadily more obscure journals) "Flagellum and Motility of Spirillum serpens," J. Bacteriol., 1953, 65:628-635;
139. "Wavelengths of Bacterial Flagella," Journal of General Microbiology, 1954, 10:452-456;
140. "Shape of Bacterial Flagella," Nature, 1955, 175:214-215;
141. "Sarcinae: Motility, Kind of Flagella, and Specific Agglutination," J. Bacteriol., 1955, 69:151-158;
142. "The Wavelengths of Helical Bacterial Flagella," J. Gen. Microbiol., 1956, 14:371-380;
143. "Genesis of Bacterial Flagella" (a film), Bacteriological Proceedings, 1956, p. 16;
144. "Bacterial Flagella and Motility," Ergebnisse der Mikrobiologie, Immunitätsforschung, und Experimentellen Therapie, 1957, 30:37-91;
145. "Reflections on Bacterial Structure," Research Council of Israel, Bulletin, Section E, 1958, 7E:115-117;
146. and "Flagella, Motility, and Agglutination of Pseudomonas viscosa." Schweiz Zeitschrift Allgemeine Pathologie und Bakteriologie, 1958, 21:707-713. Pijper's refusal to back down, right up until his death, is plain in Pijper to Weibull, 16 June 1963. My thanks to Claes Weibull for sharing a copy of this letter.
147. Olga Amsterdamska, "Stabilizing Instability: The Controversy over Cyclogenic Theories of Bacterial Variation during the Interwar Period," J. Hist. Biol., 1991, 24:191-222,
148. on p. 200. Evelyn Fox Keller's description of Barbara McClintock also seems reminiscent of Pijper. The two shared a resistance to excessive reductionism based in the "thoroughness and rigor . . . [of] virtuoso technique." See Keller, A Feeling for the Organism: The Life and Work of Barbara McClintock (New York: Freeman, 1983), p. 101.
149. Interestingly, Ludwik Fleck cites this same case to illustrate the power of what he calls a denkstihl to prevent the ability to see a phenomenon for what it is (in this case, variation among bacteria of the same species as a thing at least as common and important as their similarity to one another and to an idealized type). See Ludwik Fleck, The Genesis and Development of a Scientific Fact (Chicago: Univ. Chicago Press, 1979), p. 30.
150. The importance of this phenomenon could be gauged by considering that it was only the pursuit of the variation among pneumococci, arguably delayed until the late 1920s, which began the "trail to the double helix" as this
151. Geison, "Divided We Stand" (cit. n. 3).
152. In his report of the 1949 London meeting, N. W. Pirie seems to have found memorable the image of Pijper "returning to the sunshine" while Houwink and van Iterson returned to (presumably cloudy) Delft. See Pijper, "Bacterial Surface, Flagella, and Motility" (cit. n. 13), p. 176.
153. The Lancet writer who penned "Septem contra Pijper" (cit. n. 54), quite sympathetic to Pijper's views, said of his opponents: "We suggest that the learned doctors should, following tradition, migrate for a season to Pretoria and there enjoy sunlight microscopy and a climate which has the reputation of bracing the body and quickening the wits" (p. 89).
154. Bruno Latour, Science in Action (Cambridge, Mass.: Harvard Univ. Press, 1987), pp. 227, 236-237.
155. For a readable summary of more recent understanding of bacterial flagella and motility, especially of the burst of research in the late 1960s through the mid 1970s, see H. C. Berg, "How Bacteria Swim," Sci. Amer., Aug. 1975, 233:36-44.