550 Chapter XVII 



[674] to attack, but when the same phagocytes ingest such micro-organisms 

 as are most easily digested, such as the cholera vibrio, their action is 

 feeble. The vibrios, without any transformation into granules, re- 

 main alive for some time and are destroyed and digested with very 

 great difficulty. The cytase of the microphages, or microcytase, is 

 distinguished by other properties. It destroys and digests easily 

 many micro-organisms, but has little or no action upon the red blood 

 corpuscles and other animal cells. The exudations which are rich in 

 macrophages, such as those of the lymphoid organs, are not at all 

 or only slightly bactericidal, but exhibit a solvent action on red 

 blood corpuscles. On the other hand, the exudations, which are 

 composed in great part of microphages, leave red blood corpuscles 

 intact, but readily destroy micro-organisms. Similar properties dis- 

 tinguish the bone marrow, extracts and suspensions of which do not 

 dissolve red corpuscles, but attack micro-organisms. Now, we know 

 that the bone marrow is the principal seat of origin of the micro- 

 phages. 



Even after the addition of some of the specific fixative to the 

 microphagic exudations no solution of the red corpuscles is produced, 

 which demonstrates most clearly that the microcytase is really in- 

 capable of attacking these animal cells. 



We are, therefore, compelled to accept the existence of two 

 difierent cytases, of which one (the macrocytase) acts specially upon 

 elements of animal origin, and the other (the microcytase) acts 

 principally on micro-organisms. The indication of any more de- 

 tailed differentiations is impossible in the present state of our 

 knowledge. 



There are certain ferments which, during the life of the cells 

 which produce them, pass readily into the surrounding fluids. For 

 instance, sucrase can be recovered without difficulty from the culture 

 fluid of moulds and yeasts. The ferments of the intestinal digestion 

 also pass with great facility into the secreted fluids. Other soluble 

 ferments, on the other hand, remain very closely bound up with the 

 cells which manufacture them. Thus the zymase of the yeasts can 

 only be freed from the cells of these fungi with great difficulty, under 

 the influence of great pressure and under conditions which pro- 

 foundly alter the cell. The proteolytic ferment of the yeast is also 

 very adherent to the cells of these organisms. The fibrin-ferment, or 

 plasmase of the white corpuscles, is not secreted by these cells so 

 long as they are quite intact. But it is sufficient to subject them to 



