188G.] XEW YOKK ACADEMY OF SCIENCES. 209 



ration prevent the multiplication. This last is probably what 

 Dr. Klein adheres to, since the substance, if stable and in large 

 enough quantity to ])revent disease in the animal, would exer- 

 cise a deterring influence in cultivations outside of the body, 

 and, if not stable, would have to be constantly renewed to keep up 

 the immunity. It is then, like all the other constituents of the 

 blood and tissues, constantly elaborated and constantly destroyed, 

 the normal life action keeping it present in the right proportion. 

 This substance, then, can rightly be called normal to the blood 

 •of a pig. Is it such a substance that Dr. Klein believes prevents 

 a second attack of disease in an animal susceptible to a first? 

 His definition of such immunity negatives it ; besides, he devotes 

 a special paragrai)h to tell us distinctly it is not. To refer to his 

 definition, the first quotation from him states immunity after 

 inoculation to be due to a substance produced by the organisms 

 growing and multiplying in the first attack, Avhicli acts as a })oi- 

 son towards a second immigration. This jH-oduction, however, 

 is qualified by the words "direct or indirect," which are after- 

 wards explained by the sentence, '^ Whether this chemical sub- 

 stance has been elaborated directly by the bacilli, or whether it is 

 a result of the chemical processes induced in the body by the 

 bacilli during the first illness, matters not at all." Here then it 

 is plain that Klein would have us believe that the substance in- 

 hibitory in acqitired immunity, as compared with natural immu- 

 nity, is formed and kept stored in the former case, while con- 

 stantly replenished in the latter, and it is for this reason I have 

 denied the similarity of the two phenomena on his hypothesis. 



In discussing Pasteur's theory (the exhaustion theory), Klein 

 states that " there is absolutely no ground for the assumption 

 that if an infusion of the tissues of an animal (protected against 

 anthrax by inoculation) were made, the bacillus anthracis would 

 •not thrive in it luxuriantly ; " but surely this is equally an argu- 

 ment against Klein's own theory unless, indeed, he would claim 

 that the process of making an infusion destroyed his hypotheti- 

 cal inhibitory substance. If this claim be made, dare he assert 

 that blood directly from the circulation of a protected animal 

 will not support the multiplication of the bacillus? We think 

 the whole tenor of his work is against such a supposition. But 

 if it will not in a culture flask, why will it in the body? 



Again, all we know of the economy of the system precludes 

 the idea that such a substance could long resist the various pro- 

 cesses of absorption and elimination, and, as it is organic, we 

 may mention the possibility of oxidation in the circulation. 



The foundation of this whole theory lies in the observed fact 

 that some putrefactive organisms have been found to produce 

 in their life-processes alkaloidal and aromatic products of de- 



