316 INFECTION AND IMMUNITY 



ther digestion. Besides these germicidal bodies, there are other bodies 

 which, while not directly harmful to the bacteria, render them powerless 

 against the phagocyting power of the leucocytes. These bodies are 

 probably present in the plasma, certainly in the serum. They are the 

 opsonins or bacteriotropins. 



After phagocytosis has taken place, the germs may be killed and 

 digested. Some of the bactericidal bodies of the phagocytes are bodies 

 differing in character from the lytic bodies of the serum, and are either 

 not given off to the serum or are not active in it; but there is no proof 

 that the lytic amboceptors present in the serum are not normally, 

 in part at least, derived from the leucocytes, and active in intracellular 

 digestion when activated by complement. This is supported by the sup- 

 position that guinea-pig leucocyte extracts are not germicidal for 

 cholera and typhoid organisms. Nevertheless, intracellular digestion 

 of these germs does go on; it is possible, therefore, that the ambo- 

 ceptors present in the plasma, whatever their source, attach themselves 

 to the germs and aid in intracellular digestion. 



None of the processes just mentioned leads to the formation of anti- 

 toxins which become free in the plasma or serum. Now, in view of these 

 facts and suppositions, it may possibly be logical to conceive that nearly 

 all pathogenic germs secrete bodies which are not readily soluble in cul- 

 ture fluids or in the fluids of the animal body; that these bodies are not 

 readily, if at all, assimilable by non-phagocyting cells. These bodies may, 

 however, be broken up by digestive bodies present in the serum, and 

 from them may thus be liberated a poisonous substance, which may 

 then be assimilated by the higher cells of the body, and, when in suffi- 

 cient quantity, cause death. The more rapid the process of Hberation 

 the more quickly death ensues. This plasma digestion is, then, according 

 to this conception, a mechanism which is faulty when appKed to bacteria 

 and their products, and if this conception is correct the fault may occur 

 somewhat as follows: Bacteria and their insoluble or non-assimilable 

 products when taken into the phagocyte are subjected to two processes, 

 a primary bactericidal and coagulating one, and then a more leisurely 

 lytic or disintegrating action, during which poisonous products are 

 probably liberated, but slowly enough to be taken care of by destroy- 

 ing or neutralizing bodies. Even if the leucocyte dies, it is usually taken 

 up by a mononuclear cell, and the poisons do not become free in the 

 fluids. Now, in this process the only bodies which are produced in excess 

 and at the same time are capable of escaping from the leucocytes are the 

 /ytic bodies; neither the toxin-neutralizing body nor the coagulating 



