78 PA THOGENIC BACTERIA. 



blood in relation to its leucocytes, found that when a 

 marked experimental hypoleucocytosis was produced, the 

 bactericidal power of the blood was markedly diminished. 

 The most interesting feature of his work was the discov- 

 ery that bactericidal matter could be extracted from 

 crushed leucocytes, and that it could be subjected to a 

 temperature of 60 C. without change, thus differing 

 markedly from the alexins. 



Much discussion has arisen as to exactly what the pro- 

 tective substances are. Buchner has applied the term 

 alexin to the protective proteid substances found in the 

 blood of naturally immune animals. Hankiu has given 

 us, together with an extension of Buchner' s idea, a con- 

 siderable nomenclature of somewhat questionable utility. 

 He divides the protective substances (alexins) into sozins, 

 which occur in the blood of animals with natural immu- 

 nity, and phylaxins, which occur in the blood of animals 

 with acquired immunity. Both sozins and phylaxins are 

 divisible into two groups thus: a sozin which acts de- 

 structively upon bacteria is called a myco-sozin; one 

 which neutralizes bacterial poisons, a toxo-sozin. A phy- 

 laxin which acts destructively upon bacteria is called a 

 myco-phylaxin ; one which neutralizes bacterial toxins, 

 a toxo-phylaxui. 



The anti-microbic serums obtained by PfeifFer, Kolle, 

 Loffler, and Abel from dogs and other animals immunized 

 to typhoid fever belong in the group of myco-phylaxius. 

 The toxo-phylaxins are the antitoxins. 



5. THE THEORY OF ANTITOXINS. It is a well-known 

 fact that individuals can accustom themselves to the use 

 of certain poisons, as tobacco, opium, and arsenic, so as 

 to experience no inconvenience from what would be poi- 

 sonous doses for other individuals. This is purely a 

 matter of tolerance, but is of interest in connection with 

 the observations which are to follow. 



Ehrlich has shown that animals can tolerate gradually 

 increasing doses of ricin and abrin, provided that up to 

 a certain point the increase of dosage is very small. 



