DESCRIPTIONS OF PATHOGENIC BACTERIA. 



pecially attacked ; secondary infections with the streptococcus and 

 colon bacillus sometimes occur. 



In the second memoir Sanarelli details the results of his experi- 

 ments with the yellow fever toxin. Cultures of the germ 15-20 days 

 old, made in ordinary peptonized meat broth and filtered through a 

 Pasteur-Chamberland tube, afforded him a potent toxin. The toxin 

 thus prepared, when injected into the bodies of susceptible animals, 

 produced substantially the same symptoms as inoculation with the 

 specific bacillus. In the dog, particularly, inoculation with the 

 germ-free toxin set in motion the same train of specific symptoms 

 and caused the same pathological changes in the tissues. "The 

 toxin of yellow fever is an exceedingly powerful cellular poison com- 

 parable solely, in some points, to the diphtheria toxin. Its contact 

 with the tissue elements of the animal organism, especially the higher 

 species, determines, like that of the diphtheria toxin, a violent irrita- 

 tion, followed by retrogressive processes which always end in the 

 necrosis and fatty degeneration of the protoplasm." 



Some very interesting experiments bearing on the question of 

 mixed infection are next described. When B. icteroides is sown 

 upon culture media on which, the colon bacillus, streptococcus and 

 proteus respectively, have been previously grown, it is found that 

 the growth of the former is distinctly inhibited by the presence of the 

 soluble products of the other microbes. The latter, on the contrary, 

 grow excellently in a medium previously inhabited by B. icteroides, 

 and are only slightly incommoded by the presence of the soluble 

 products of one another, the products of the proteus bacillus seem- 

 ing most injurious to all concerned. A similar result was revealed 

 by a study of the ' vital antagonism ' of B. icUroidesvaA the microbes 

 concerned in the secondary infections. Both Streptococcus pyog, and 

 Staphylococcus pyog. an. speedily gain the upper hand over B. icter- 

 oides, and a similar, though less marked superiority, is manifested by 

 the colon bacillus. These facts certainly shed much light on the 

 difficulty of demonstrating the presence of the yellow fever germ in 

 the bodils of victims of the disease, and go far to explain the nega- 

 tive result reached by many observers. 



In an attempt to account for the important part played by mari- 

 time commerce in the diffusion of yellow fever, Sanarelli records 

 a curiously significant observation. It was noticed that gelatin 

 plates sown with B. icteroides sometimes remained without develop- 

 ment, although agar plates sown at the same time evinced abundant 

 growth. But if a colony of mould made its appearance on the 

 gelatin plate, colonies of B. icteroides immediately sprang up around 



