PHAGOCYTOSIS 187 



return in greatly increased numbers and undertake the destruction of 

 the foreign substance. If this substance be sterile no great harm is 

 likely to result. The surgeon leaves catgut sutures in the tissues, but 

 if they be sterile the phagocytes eat them entirely and no harm comes. 



Among the several kinds of white blood corpuscles, the large mono- 

 nuclear cells are most effective in feeding on animal cells, whether 

 native or foreign to the body, and are designated by MetchnikofT as 

 macrophages. The polynuclear leukocytes play a more important role 

 in bacterial infection and are denominated microphages. The former 

 are able to engulf and completely digest a large number of cells. If 

 lymph glands, the great omentum or the spleen be crushed, ground in 

 a mortar and extracted with salt solution, a fine emulsion is obtained, 

 and this dissolves the red corpuscles of various vertebrates. This 

 hemolytic action is destroyed by a temperature of 56 C. continued for 

 one hour, and at 60 C. in a shorter time. This thermolabile ferment 

 is the cytase of Metchnikoff, the alexin of Buchner, and the comple- 

 ment of Ehrlich. It should be stated that the emulsion of macro- 

 phages contains other and thermostabile hemolytic agents, such as 

 fatty acids and soaps, but with these we are not concerned at present. 



Bordet showed that the ferment obtained from the macrophages 

 is a complex body consisting of two parts. One is thermolabile, the 

 other thermostabile. One combines with red corpuscles even at low 

 temperature, but does not dissolve them until the other enters into the 

 reaction. Bordet calls the thermostabile body the sensitizer. It pre- 

 pares the red corpuscles for the action of the complement. Ehrlich 

 names the thermostabile substance the amboceptor, combining by one 

 hand with the red corpuscle and by the other with the complement. 

 Bordet's conception is that the action of. the sensitizer is a physical one 

 similar to that of a mordant ; Ehrlich's is that of a chemical combina- 

 tion. It is needless to go into a discussion of this difference since all 

 agree that the ferment consists of a thermostabile and a thermolabile 

 part and that joint action is necessary to induce hemolysis or other 

 cytolysis. The alexin or complement does not combine with the red 

 corpuscle or foreign cell directly, and does so only through the sensi- 

 tizer or amboceptor. In his later papers, Metchnikoff retains the term, 

 cytase, for the thermolabile body and adopts the term, fixator, for the 

 thermostabile substance. 



