218 PHYSIOLOGY. 



The lock and key simile of E. Fischer affords perhaps the best 

 analogy. The lock is the cell, the key is the amboceptor, and the 

 hand which turns the key is the complement. The macrophages attack 

 the xanthocytes, or large animal cells, and malarial parasites. The 

 microphages prefer the bacteria of acute diseases. The complement 

 occurs in normal animals, the amboceptor is developed. 



Haamolysins are derived from the leucocytes. Bacteriolysins 

 are contained in the euglobulin fraction of the serum. 



Enterokinase acts like an amboceptor, uniting the red corpuscles 

 of the blood to trypsinogen, which behaves like a complement and 

 dissolves the red blood-corpuscles. 



The toxic action of cobra-poison upon red blood-corpuscles 

 depends upon the combination of amboceptors, intermediary bodies 

 contained in the venom, with corresponding complements contained, 

 not in the venom, but in the cells or fluids of the animal acted upon. 

 Kyes, working with cobra-venom found an endo complement con- 

 tained in the red corpuscles themselves. Kyes also found that 

 lecithin is capable of combining with venom intermediary and thus 

 completing the haamolytic potency of venom. Here is a cytotoxin 

 formed of an intermediary body and a definite crystallizable sub- 

 stance uniting with it, thus acting as a complement. Here we have 

 a poison in our own body, only needing the intermediary body of 

 the venom to act upon us. Snake-poison only contains one-half of 

 the complete poison. Rattlesnake-poison has been found by Flexner 

 and Noguchi also to contain another cytotoxin which has the power 

 to dissolve endothelial cells, an endotheliallysin. 



It is an important function of the mother to transfer to the 

 suckling, through her milk, immunizing bodies, and the infant's 

 stomach has the capacity, which is afterwards lost, of absorbing these 

 substances in the active state. The relative richness of the suckling's 

 blood in protective antibodies, as contrasted with the artificially fed 

 infant, explains the greater freedom of the former from infectious 

 disease. 



OPSONINS. 



There is in normal serum, a substance which so acts upon bac- 

 teria as to render them susceptible of being devoured by the leuco- 

 cytes. In some way serum stimulates phagocytosis by making the 

 bacteria more susceptible of being absorbed by leucocytes. This 

 substance in the serum has been denominated by Wright and 

 Douglass, opsonin (feast-preparer). 



