THE WAR WITH THE MICROBES., 491 



during tlie life of the latter. As the germs die, however, in artificial 

 cultures, the cell walls gradually disintegrate an(l the poison passes 

 out into the surrounding liquid. In the case of tuberculosis and glan- 

 ders 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 animals and thus preventing the 

 spread of untold evils. 



Thus the warfare, first begun 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 charac- 

 ter of the insidious poisons with which their arrows are tipped. To a 

 certain extent, 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 appar- 

 ent. While Jenner, in vaccination for smallpox, and "Pasteur, with his 

 method of vaccination for anthrax, had shown that it was possible to 

 protect animals and men from a virulent attack of disease by giving 

 them first a mild attack (though, by the way, there are a few who con- 

 tend even to day that vaccination is useless), it remained for Salmon, 

 his assistant, and Smith, in this city, to demonstrate, in 1882, that the 

 j)oisons 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 animal a small 

 quantity of the poison of the germ, so that when the germ itself was 

 injected 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 vaccination was tried for diphtheria, tetanus, 

 anthrax, cholera, typhoid fever, tuberculosis, glanders, and a number 

 of other diseases. But this discovery led to another, important and 

 far-reaching. Fodor showed that the blood serum of animals made 

 immune to a particular disease by injecting the animal with the poison 

 which this germ formed had the effect of destroying the germ of the 

 disease. This excited renewed interest in the study of the blood, and 

 within a few years it was demonstrated by the work of many, some in 

 this city in the laboratory before mentioned, that this serum from pre- 

 viously immunized animals not only had the property of conferring 

 immunity upon other animals, but also of checking the disease after it 

 had once begun. How thoroughly this fact was demonstrated, first 

 by Behring and subsequently by Eoux and others, in connection 

 with diphtheria and tetanus has been dwelt upon often, and we know 

 of the many thousands of lives that have been saved by the use of 

 antitoxic serums. 



