Summary 549 



fever and the Trypanosomata. The macrophages can also ingest 

 the bacteria of acute diseases, but, save in exceptional cases, their 

 intervention is of little moment. 



The raicrophages, on the other hand, appear to play their part [573] 

 specially in acute infections. Their intervention against animal cells 

 is nil, or almost so. Thus they rarely seize the red corpuscles of 

 the same or of a foreign species of animal. They also appear to be 

 repelled by parasites of animal origin and by certain bacteria which 

 set up chronic diseases. Whilst the macrophages seize the bacilli 

 of leprosy with great avidity, the microphages ingest them only 

 exceptionally. 



The morphological and physiological differences between the two 

 great categories of mobile phagocytes (leucocytes), correspond to 

 differences in the composition of their soluble ferments. Just as the 

 Amoebae digest their prey by means of their amoebodiastase, a 

 soluble ferment of the group of trypsins, so the white corpuscles 

 submit the foreign bodies ingested by them to the action of what are 

 now known as cytases. These cytases (alexins or complements of 

 other writers) are soluble ferments which also belong to the trypsin 

 group. They act in a medium which is feebly acid, neutral, or feebly 

 alkaline, and, like the amoebodiastase, they are distinguished by a 

 great sensitiveness to heat. When the cytases are contained in fluids, 

 a temperature of 55 56 C- destroys them rapidly and completely. 

 When they are found in organs reduced to the state of an emulsion, 

 their sensitiveness diminishes and it is necessary to raise the tempera- 

 ture to 58 62 C. in order to destroy their activity. 



Bordet maintains that the cytases are very different in the various 

 species of animals, but that in the same species only one cytase 

 exists. Ehrlich and Morgenroth, on the other hand, hold that the 

 same serum contains several, sometimes many, different cytases. 

 This question is too difficult to be definitely solved at present. It 

 appears to me very probable that there exist, in the same species of 

 animal, two different cytases. One of these, the macrocytase which 

 is found in the lymphoid organs and in the serum of the blood, acts 

 more particularly on animal cells. Thanks to this substance an 

 extract or maceration of the spleen, omentum or lymphatic glands 

 dissolves the red blood corpuscles more or less readily ; these extracts 

 and macerations, however, are incapable of destroying bacteria. 

 When the macrophages seize the nucleated blood corpuscles they 

 digest them completely, not sparing even the nucleus, so resistant 



