556 Chapter XVII 



say, in the spleen, lymphatic glands, and bone marrow, at a period 

 [580] when there was, as yet, none in the blood. This fact has been 

 extended to other examples of fixatives of micro-organisms, and it 

 cannot be questioned that the phagocytes produce these soluble 

 ferments. Under the influence of the introduction of micro-organisms 

 into the body, a phagocytic reaction is produced which has, as a 

 consequence, the digestion of these micro-organisms and the pro- 

 duction of corresponding fixatives. There is every reason to believe 

 that, in these cases, it is the microphages which, seizing and 

 digesting the micro-organisms, produce the fixatives. 



But the macrophages are also capable of producing these ad- 

 juvant ferments. Even in normal animals the macrophagic organs, 

 such as the spleen, and especially the mesenteric glands, contain 

 fixatives which help in the solution of the red blood corpuscles. 

 Into this group of facts we must also place the production by the 

 mesenteric glands, as well as by certain other lymphoid organs, 

 and the leucocytes of exudations and the blood, of enterokynase, 

 the soluble ferment which aids the digestive action of trypsin. 

 This enterokynase is also a species of fixative ; it permeates the 

 flakes of fibrin and renders them much more accessible to the in- 

 fluence of the trypsins. 



The fact that the enterokynase of the intestinal digestion corre- 

 sponds in so many respects to the fixatives which act in the 

 absorption of formed elements in general and of micro-organisms 

 in particular, furnishes a further proof that the destruction of micro- 

 organisms in the animal is an act similar to true digestion. 



Phagocytes, those elements which accomplish the absorption of 

 micro-organisms and of animal cells, those holders of digestive 

 cytases, are also the manufacturers of fixatives. Having brought 

 about this absorption, the phagocytes set to work to elaborate large 

 quantities of fixatives, although they are unable to increase the 

 amount of cytases in any marked degree. The fixatives, produced 

 in abundance, can be excreted outside the phagocytes and pass into 

 the blood plasma, and, with it, into the fluids of exudations and 

 transudations. But this excretion is not an indispensable act for the 

 functioning of the fixatives. As these ferments prepare the way 

 for the digestive action of the cytases, it is necessary only that they 

 should be able to fix themselves on the formed elements before the 

 latter. It is, therefore, easy to explain cases of acquired immunity 

 in which no fixatives are found in the body fluids. Such examples 



