566 



SCIENCE. 



[N. S. Vol. V. No. 119. 



separating from cultures of the tuberculosis 

 germ a crystalline poison with constant 

 melting point and a constant composition. 

 This is not the only poison produced by the 

 tuberculosis germ, but that it is one of the 

 principles which is responsible for much of 

 the trouble with this disease is beyond 

 doubt. These special poisonous principles, 

 which are so difBcult to obtain pure, we 

 designate by the name toxines, to distin- 

 guish them from the ptomaines and proteid 

 substances before mentioned. Another dif- 

 ficulty which is always encountered in ex- 

 tracting the poisons of bacteria is their in- 

 stability. The material with which an ex- 

 periment is begun may be very poisonous, 

 but the processes of precipitation and ex- 

 traction through which it must be passed in 

 order to obtain a desired substance are such 

 that often, long before the final stages have 

 been reached, the nature of the poisons has 

 undergone an entire change due to the 

 chemical processes which have necessarily 

 been applied. 



We have said that the poisons of the 

 germ were synthetic products which were 

 built up within the cell wall. Some of 

 these easily pass through the cell wall, due 

 probably to the greater permeability of the 

 living membrane ; others are retained within 

 the cell wall only to pass into solution when 

 these walls are broken down. Tetanus, 

 diphtheria and swine plague allow this dif- 

 fusion to take place very rapidly, while 

 with other germs, like typhoid fever, an- 

 thrax, cholera, glanders, tuberculosis, the 

 poison is produced and retained within the 

 cell more firmly during the life of the latter. 

 As the germs die, however, in artificial cul- 

 tures, the cell walls gradually disintegrate 

 and the poison passes out into the surround- 

 ing liquid. In the case of tuberculosis and 

 glanders a strong solution of these cell 

 poisons in the surrounding liquid upon 

 which the germ has been feeding gives 

 tuberculin and mallein, the two diagnostic 



agents which have been of inestimable value 

 in detecting latent disease in men and ani- 

 mals and thus preventing the spread of un- 

 told evils. 



Thus the warfare first began by the 

 chemist with the microbes in identifying 

 their character and relation to disease has 

 been prosecuted for little more than a 

 decade in endeavoring to detect the true 

 character of the insidious poisons with which 

 their arrows are tipped. To a certain ex- 

 tent, as we have seen, this warfare has 

 been a successful one in so far that the 

 poisons have been hunted and driven to 

 their last stronghold, which, ere long, with 

 the many workers in attack, must yield as 

 heretofore to superior forces. But while 

 this search for the pure poisons has been in 

 progress the chemist has not been idle in 

 endeavoring to counteract these poisons, 

 the nature of which he did not thoroughly 

 understand, but the evil effects of which 

 were only too apparent. While Jenner in 

 vaccination for small-pox, and Pasteur with 

 his method of vaccination for anthrax, had 

 shown that it was possible to protect ani- 

 mals and men from a virulent attack of 

 disease by giving them first a mild attack, 

 (though, by the way, there are a few who 

 contend even to-day that vaccination is use- 

 less), it remained for Salmon, his assistant, 

 and Smith in this city to demonstrate, in 

 1882, that the poisons of germs could be 

 used by men and animals to fortify them- 

 selves against the attacks of these same 

 bacteria. This could be accomplished by 

 introducing into the circulation of the ani- 

 mal a small quantity of the poison of the 

 germ, so that when the germ itself was in- 

 jected the poison which it produced was 

 without effect. What had been found true 

 for one disease of animals proved also to be 

 true for many others, and chemical vaccina- 

 tion was tried for diphtheria, tetanus, an- 

 thrax, cholera, typhoid fever, tuberculosis, 

 glanders and a number of other diseases. 



