Lnicholls] unsolved PROBLEMS OF IMMUNITY 26S 



regard to this point have failed to show any constant relationship 

 betw^cen the two factors. "With certain drugs, such as sodium cinna- 

 mylicum and tallianine, which produce marked leucocytosis, no increase 

 in opsonin could be made out. AVith the nuclein of yeast, however, 

 they observed a notable increase in the opsonic content, often unasso- 

 ciated with any increase in the leucocytes. Huggard and Morland, 'On 

 the other hand, found that the internal administration of yeast led to 

 an increased output of opsonins as well as a marked leucoc3^tosis. This 

 is an interesting scientific explanation of the efficacy of a certain empir- 

 ical line of treatment of infection in vogue in certain countries, notably, 

 France, namely, the treatment of furunculosis with brewer's yeast. 



The doctrine of "' opsonins " gives us a working basis on which 

 to explain some at least of the phenomena of infection. "WTien bac- 

 teria gain an entrance into the economy some of them are immediately 

 sensitized by the plasma and are thereupon engulphed by the phago- 

 cytes. The amount of the immune substance available is, however, small 

 and the supply soon exhausted. Consequently, if more micro-organisms 

 be present than it is able to deal with, they will multiply and be 

 either indifferent to the phagocytes or exercise a repelling influence 

 upon them (negative chemotaxis), there being no free immune bodies 

 present. 



The activity of the opsonins is, however, but one phase of the 

 reaction against infection. As before mentioned, there are several 

 other substances in blood serum which exert defensive powers. In 

 the case of cholera and typhoid fever, Pfeifl'er showed that the specific 

 germs of these diseases when subjected to the action of immune serum 

 were first agglutinated rendered motionless (Pfeiifer's phenomenon) 

 and eventually -dissolved (bacteriolysis). Such immune sera, therefore, 

 contain two sulistances, agglutinins, which clump the bacteria, and 

 lysins, which dissolve them. It used to be thought that the phenomenon 

 of agglutination was a necessary part of bacteriolysis, but this is not 

 the case. A serum that is both agglutinative and bacteriolytic may 

 be deprived of the latter property without detriment to the former. 

 Lysins are, therefore, different from agglutinins. It is rather singular, 

 perhaps, that lysins cannot be always demonstrated to be present in 

 cases of infectious disease. This, however, simply indicates the great 

 complexity of Nature's processes and proves that the same end may 

 be achieved in a variety of ways. In this sphere, also, apparently, 

 more than one road loads to Eome. Similar!}^, antitoxins, which are 

 so potent a factor in the case of certain infections, as, for example, 

 diphtheria, cannot always be detected. AMiy these marked differences 

 in different cases we are at a loss to know. It would seem as if there 



