356 INFECTION AND IMMUNITY. 



to dissolve the bacteria. The complement may be 

 present in the serum which is injected, or the nat- 

 ural complement of the individual may be utilized 

 by the amboceptors. 



comparison When one seeks to compare the theory of Ehrlich 

 with that of Metchnikoff one finds little more in 



" common than the general purpose of explaining 

 the phenomena of immunity. Yet it is remark- 

 able that where there is so little in common there 

 are so few contradictions of an essential nature. 



The theory of Ehrlich has that degree of defi- 

 niteness which it must have in order to be a plausi- 

 ble chemical theory, whereas that of Metchnikoff 

 seems more general in that it is so largely biologic 

 and vitalistic. 



Each has a certain relation to nutrition. Phago- 

 cytosis as a nutritional measure is found in lower 

 types of animals, and accomplishes nothing further 

 than to bring the food substance in contact with 

 the digestive ferments contained in the cell. In 

 relation to nutrition the theory of Ehrlich begins, 

 so to say, where the phagocytic theory leaves off, 

 involving, as it does, the method by which food 

 substances become a part of the protoplasm. 



Metchnikoff, with Ehrlich, recognizes the vari- 

 ous antibodies which have been discovered. The 

 former holds that all are produced by the phago- 

 cytes without suggesting clearly a method by 

 which they may be formed. Ehrlich assumes a 

 very precise method by which they may be formed, 

 but designates no particular cells as their pro- 

 ducers, stating only in a general way that an anti- 

 body is produced only by those cells with which the 



