BACILLUS PERTUSSIS 235 



end to end; it is non-motile. It stains faintly with the aniline 

 dyes. Bi-polar bodies which stain more deeply than the center of 

 the organism can sometimes be distinguished. It is decolorized by 

 Gram's method. 



Cultivation. The organism grows feebly at first even on the 

 medium especially recommended by Bordet and Gengou, consist- 

 ing of 1 per cent glycerin mixed with macerated potato and an 

 equal quantity of human or rabbit blood. After several genera- 

 tions it will grow moderately well on veal agar or broth. The 

 organism is an aerobe and develops best at 37 C. 



Pathogenesis. A mild toxin is undoubtedly produced and 

 absorbed, but of more importance is the mechanical disturbance 

 caused by the bacilli in the respiratory tract. They have been 

 described as being present in enormous numbers in the trachea, 

 packed between and clinging to the cilia of the epithelial cells. 

 This according to certain investigators constitutes the specific 

 lesion of whooping cough. B. pertussis has not yet been definitely 

 proved to be the specific cause of the disease, although much evi- 

 dence has been advanced in favor of the theory. Its strongest 

 claim to recognition is the fact that in the serum of convalescents 

 a specific antibody is produced which gives a positive complement 

 fixation reaction with the organism. 



BACILLUS OF SOFT CHANCRE 



The bacillus of soft chancre or chancroid was obtained in pure 

 culture by Ducrey in 1889 from the purulent discharge of an 

 ulcerated surface. 



Morphology and Staining. The organism is exceedingly small, 

 measuring about 1.5 /^ in length and 0.5 ^ in width. In tissue 

 sections it usually appears attached in long chains or grouped 

 together in masses. It is non-motile and does not form spores 

 and is Gram negative. Stained with carbol fuchsin deeply colored 

 bi-polar bodies can often be distinguished. 



Cultivation. The best medium for cultivation has been found 

 to be a mixture of agar and rabbit's blood in the proportion of 



