HERBERT C. WARD n 



granules and both small and large spirochetes representing every gradation in size 

 from granules to normal adult spirochetes. While he did not observe the actual growth 

 of granules into spirochetes, he concluded from the varying numbers of granules and 

 spirochetes that the change must occur in this direction. Balfour described a special 

 type of spirochete concerned with fowl spirochetosis which he named S pirochaeta 

 granulosa penetrans, and which he believed entered the red-blood corpuscles of the 

 fowl and broke up into granules that were responsible for a peculiar recrudescence of 

 the disease known as the ''after-phase." There can be Uttle doubt that granules are 

 produced in a number of both pathogenic and saprophytic spirochetes, and are shed 

 from the cells under certain circumstances. That granules are reproductive elements 

 cannot be regarded as settled since Button and Todd have shown that adult spiro- 

 chetes can sometimes be found on prolonged search in infective ticks along with the 

 granules. Filtrates from spirochetal material showing an abundance of granules may 

 also reveal a few spirochetes which because of their peculiar boring motility are able 

 to pass through the filter substance. Recently Meirowsky" has observed swollen 

 bodies and coiled forms in Treponema pallidum in secondary syphilis and has suggested 

 that they are stages in the life-history of the organism. Szilvasi and Feher^ have found 

 Meirowsky's forms in both primary and secondary lesions in syphilis and agree with 

 him in regarding them as infective stages of the treponema. It may be noted in this 

 connection that Aristowsky and Holzer-' have described peculiar coiled, twisted forms 

 in Spirochaeta ohermeieri and believe that this organism also passes through a defi- 

 nite life-cycle. 



THE RICKETTSIAE 



Following the discovery of pleomorphic bacteria-like bodies in Mexican typhus 

 (tabardillo) by Ricketts a number of similar organisms were observed in various dis- 

 eases and in their insect vectors. For this group the term "Rickettsia" was proposed 

 by Da Rocha-Lima'' and the type species named Rickettsia prowazeki in honor of 

 Ricketts who discovered the first representative and von Prowazek who devoted 

 many years to its investigation. The significance of this group of micro-organisms 

 will be considered in chapter xxxix of this volume, but one or two points should be 

 mentioned here in regard to their morphology. Hertig and Wolbach^ and Cowdry^ in 

 this country have noted their wide distribution in insects and arachnids. According to 

 Arkwright, Atkin, and Bacot,^ the rickettsiae are characterized by their minute size, 

 usually being less than 0.5 /x in diameter; their pleomorphism from round, coccus-like 

 bodies and diplococci to minute bacilli and threadlike forms; their resistance to or- 

 dinary aniline stains; their loss of gram stain and affinity for Giemsa; their absence of 

 motility; their resistance to cultivation on ordinary media; and their occurrence in very 

 large numbers in the gut of blood-sucking insects. In some cases they may be found 



' Meirowsky, R.: Mimchen. med. Wchnschr., 60, 1870. 1913. 

 'Szilvasi, J., and Feher, D.: Cenlralbl. f. BakterioL, 95, 436. 1925. 



3 Aristowsky, W., and Holtzer, R.: ibid., p. 175. 1925. 



4 Da Rocha-Lima: Miinchen. med. Wchnschr., 67, 1381. 1916. 



5 Hertig, M., and Wolbach, S. B.: J. Med. Research, 44, 329. 1924. 

 ^Cowdry, E. V.: J. Exper. Med., 37, 431. 1923. 



'Arkwright, J. A., Atkin, E. E., and Bacot, A.: /. ParasiloL, 13, 27. 1921. 



