IMMUNITY AND SUSCEPTIBILITY. 81 



minority of scientists, that the antitoxin is the toxin in 

 a modified (oxidized ?) form, and supports his view by 

 the fact that the antitoxins are specific for their respec- 

 tive toxins only, and by quoting the experiments of 

 Kondrevitsky, who, killing animals two hours after 

 an injection of toxin, found in the blood toxin alone ; 

 killing later, found some antitoxin, and still later much 

 antitoxin. 



The difference between this theory of neutralization 

 by antitoxins and Chaveau's retention-hypothesis is quite 

 marked. The retention-theory teaches that a bacterium 

 leaves behind it a substance prejudicial to its future 

 growth in the economy a distinct metabolic product. 

 The antitoxic theory shows the protective substance to 

 be a product not of bacterial growth, but of tissue-energy, 

 not depending upon the presence of the bacteria, but 

 upon the presence of a poison. 



The antitoxins do not usually act harmfully upon the 

 bacteria, or preclude their growth in the animal body, but 

 prevent their pathogenesis by annulling their toxicity 

 i. e., enabling the body-cells to endure the injury and 

 placing them in a position exactly parallel with non- 

 pathogenic bacteria. 



Closely related to the antitoxins, if not identical with 

 them, are certain substances of an anti-infections nature 

 that can be generated in the blood of animals to which, 

 in the process of immunization, the bacteria, instead of 

 their poisons, have been administered. The anti-infec- 

 tious serums are protective against the bacterial infections, 

 but powerless against the toxins. They are the only 

 results of immunization against cholera and typhoid 

 fever. When antitoxic serums can be secured they are 

 of far greater importance, and should always be selected 

 for purposes of therapeutics. 



The diseases which are at present controllable by anti- 

 toxins are toxic diseases, caused by the entrance of toxin- 

 producing bacteria into the body. The growth of these 

 toxin-producers probably depends upon the inability of 



