374 BIOLOGY: GENEBAL AND MEDICAL 



enzymic substances, and that if the phagocytes were 

 destroyed the enzymes remained in solution in the body 

 juices. The alexine of Buchner was, in his opinion, 

 microcytase, an enzyme resulting from phagolysis, or 

 dissolution of the phagocytes. 



By an ingenious manipulation, he contrived to place 

 bacteria, inclosed in small collodion bags, in the body 

 cavities of animals. These microorganisms, though 

 exposed to the effects of the body juices, were defended 

 from the phagocytes and multiplied abundantly, though 

 if the bag ruptured they were destroyed by the cells. 



In the meantime, the toxins and antitoxins had been 

 discovered, and it became necessary to account for im- 

 munity against intoxication and for antitoxin formation. 

 The theory was, however, capable of application to the 

 new problems, for, it was argued, not only may the 

 phagocytic cells take up formed objects, but they may 

 also absorb fluids, and by virtue of their enzymes, digest 

 and destroy the toxins they contain. Further, the 

 enzymes liberated from destroyed phagocytes may be 

 capable of acting similarly upon free toxin in the blood. 



Each toxin injection administered to an animal was 

 supposed to destroy innumerable phagocytes, with whose 

 enzymic contents the blood became replete, hence its 

 antitoxic character. 



It was sometimes difficult to substantiate the views 

 of the theorist, but time usually brought forth new and 

 surprising evidences in his favor. 



Two kinds of phagocytes were next found to be im- 

 portant, the leucocytes or microphages, possessing an 

 enzyme called microcytase, and the tissue cells, notably 

 the endothelial cells or macrophages, possessing an enzyme 

 called macrocytase. 



The bacteria and minute entities are taken up by the 

 microphages, larger objects, like heterologous blood 

 corpuscles, suspended tissue fragments, etc., by the 

 macrophages. The action of the two enzymes is slightly 

 different. 



