FUSIFORM BACILLI AND SPIRILLUM FUSIFORMIS 605 
hebdomadis is strikingly like Leptospira icterohieniorrhagiae. It 
is differentiated serologically from the latter by cross inmnmization 
experiments in guinea-pigs, and by Pfeift'er's phenomenon, in which 
convalescent serum from human cases and the specific organism fail 
to infect these animals. 
Guinea-pigs immunized to Leptospira icteroha^morrhagise are sus- 
ceptible to infection with Leptospira hebdomadis, but not to the 
homologous Leptospira and rice versa. 
An accidental infection of man with a hypodermic needle charged 
with organisms from a guinea-pig resulted in a typical attack of 
seven-day fever, thus pointing to the etiological relationship of the 
organism. 1 The urine, but not the feces or sputum of human cases, 
was found to contain the infective agent. 
FUSIFORM BACILLI AND SPIRILLUM FUSIFORMIS. 
Fusiform bacilli, frequently in association with spiral organisms, 
have been observed by Plant- and Vincent^ in diphtheroid angina; 
by Vincent^ in cases of hospital gangrene; by Bernlieim^ in stomatitis 
ulcerosa and angina ulcerosa; in noma'^ and in erosive and gangrenous 
balanitis bv Corbus.^ 
Fig. 83. — Vincent's angina, Bacillus and Spiiillum fusiformis. 
The organism, B. fusiformis, is a long, thin bacillus with distinctly 
tapering ends measuring from 0.5 to 0.8 micron in diameter at the 
center, and varying in length from 3 to 10 microns. The bacilli appear 
to be rigid and straight as a rule, but occasional rods are observed to be 
slightly curved. In fluid media there is a tendency for the organisms 
1 Ido, Ito and Wani: Loc. cit. 
2 Deutsch. med. Wchnschr., 1894, 20, 920. 
3 Ann. Inst. Pasteur, 1899, 13, 609. 
" Ibid., 1896, 10, 488. 
5 Centralbl. f. Bakteriol., 1898, 23, 177. 
6 Brault: Bull, dermat. et syph., 1908, p. 2. 
• Jour. Am. Med. Assn., 1913. 60, 1769. 
