260 SUSCEPTIBILITY AND IMMUNITY. 



ments Ehrlich used blood serum from an immune horse to give im- 

 munity to the mother mouse when her young were already seven- 

 teen days old. Of this blood serum two cubic centimetres were 

 injected at a time on two successive days. The day after the first 

 injection one of the sucklings received a tetanus inoculation by 

 means of a splinter of wood to which spores were attached. The 

 animal remained in good health, while a much larger control mouse 

 inoculated in the same way died of tetanus at the end of twenty-six 

 hours. Other sucklings, inoculated at the end of forty-eight and of 

 seventy-two hours after the mother had received the injection of 

 blood serum, likewise remained in good health, while other control 

 mice died. 



A most interesting question growing out of these extraordinary 

 experimental results at once presents itself : Does the animal which 

 is immune for one of these toxalbumins also exhibit immunity as re- 

 gards the toxic action of the other ? This question Ehrlich has an- 

 swered. His experiments show that animals which are immune 

 against one of these substances are quite as susceptible to the toxic 

 action of the other as if they did not possess this immunity i.e., the 

 antitoxine of ricin does not destroy abrin, and vice versa. As an 

 illustration of this fact he states that in one experiment a rabbit was 

 made immune against ricin to such an extent that the introduction into 

 its eye of this substance in powder produced no inflammatory reac- 

 tion ; but the subsequent introduction of a solution of abrin of 

 1 : 10,000 caused a violent inflammation. 



Evidently these facts are of the same order as those relating to 

 immunity from infectious diseases, and, taken in connection with the 

 experimental data previously referred to, give strong support to the 

 view that the morbid phenomena in all diseases of this class are due 

 to the specific toxic action of substances resembling the toxalbumins 

 already discovered ; and that acquired immunity from any one of 

 these diseases results from the formation of an antitoxine in the body 

 of the immune animal. 



Hankin calls these substances produced in the bodies of immune 

 animals " defensive proteids," and proposes to classify them as fol- 

 lows : First, those occurring naturally in normal animals, which he 

 calls sozins ; second, those occurring in animals that have acquired 

 an artificial immunity these he calls phylaxins. Each of these 

 classes of defensive proteids is further subdivided into those which 

 act upon the pathogenic microorganism itself and those which act 

 upon its toxic products. These subclasses are distinguished by the 

 prefixes myco and toxo attached to the class name. 



In accordance with this classification a mycosozin is a defensive 



