Summary 559 



animal the fixatives are found more especially in the phagocytic 

 organs. The leucocytes which digest gelatine exhibit in an even [583] 

 more distinct fashion the modification of these cells in animals which 

 have received several injections of gelatine. The leucocytes of exuda- 

 tions, when the fluid is removed, become much more fitted to digest 

 the gelatine than they were at first. 



A similar adaptation is also observed in intestinal digestion, which 

 may serve as a fresh point of comparison between the intracellular 

 digestion of the phagocytes and the extracellular digestion in the 

 intestines. The pancreas, in order to secrete its soluble ferments, adapts 

 itself to the nature of the food which passes into the digestive canal. 



The fixatives are not the only soluble ferments which appear in 

 large quantities in the fluids of the immunised animal. Very often 

 there are found along with them substances which agglutinate the 

 micro-organisms in animals which have received several injections of 

 micro-organisms of the same or an allied species. The same fact 

 is observed in animals treated with animal cells. Thus the fluids 

 of animals injected with blood corpuscles become agglutinative for 

 these corpuscles. 



The analogy between the agglutinins and the fixatives is so great 

 that for some time several observers assumed them to be one and 

 the same substance. This can no longer be upheld, for it is clearly 

 demonstrated that the property of the body fluids to agglutinate 

 micro-organisms and animal cells is difierent from that which brings 

 about their permeation by fixatives. The agglutinins resist the 

 same temperatures as the fixatives ; both are specific to the same 

 degree and pass equally from the cells which produce them into the 

 plasmas of the blood, lymph, exudations, and transudations. The 

 agglutinins capable of clumping the formed elements into masses 

 may, under certain conditions, render their ingestion by the phago- 

 cytes more easy. In general, however, the part played by the 

 agglutinins in acquired immunity must be regarded as of little 

 importance, and for that reason we abstain from basing any theory 

 of this immunity on the agglutinative property of the body fluids. 

 Besides fixatives and agglutinins, the fluids of an animal which has 

 acqiured immunity very probably possess other properties which 

 must have a greater or less function in acquired immunity. Thus, 

 we are often struck by the stimulating action of these fluids on the 

 normal animal into which they are introduced. This stimulation is [584] 

 especially manifested against tiie phagocytic reaction. 



