312 INFECTION AND IMMUNITY. 



may choose to put in contact with leucocytes so 

 stimulates or injures them that they discharge cer- 

 tain of their constituents. If the fixators and 

 Liberation cvtase are among the constituents which are dis- 



of Cytase by " n ,-, , ,-, .... . -, .-, 



choTged at the time the injection is made, the 

 extracellular hemolysis encountered in the experi- 

 ment described above might depend on the libera- 

 tion of these substances rather than on their nat- 

 ural occurrence in the plasma. If this be true, 

 and if one could in some way fortify the leucocytes 

 against phagolysis, the plasma would remain free 

 from hemolytic power. Metchnikoff accomplishes 

 such fortification, i. e., prevents phagotysis, by a 

 simple procedure, which demands nothing more 

 than the peritoneal injection of a small quantity 

 of bouillon or salt solution twenty-four hours in 

 advance of the experiment. Possibly by this 

 means the leucocytes have been habituated to the 

 presence of a foreign fluid, or the new leucocytes 

 which accumulate possess greater resistance. What- 

 ever the explanation, the erythrocytes which are 

 injected at this critical time are said not to un- 

 dergo extracellular hemolysis, but instead are en- 

 globed and dissolved by the macrophages. These 

 results and others of a similar nature are the basis 

 for the belief that cytase normally is intracellular, 

 and that it becomes extracellular only when the 

 leucocytes are subjected to injurious influences. 

 The fact that the serum of defibrinated or coagu- 

 lated blood contains cytase is not in discord with 

 such an opinion, for in this instance also the leu- 

 cocytes may be injured to such a degree that cer- 

 tain of their constituents are discharged. We are 



