2/6 PHYSIOLOGICAL CHEMISTRY. 



ins are all complex aggregations of more or less complex mole- 

 cules. The latter have certain configurations dependent on the 

 presence of side chains or side groups, to borrow an expres- 

 sion from organic chemistry. These side chains are directly 

 or indirectly the points of attack or defense in the action of 

 the several bodies on each other. In order that a substance 

 may act as an enzymic poison or toxin to cells of the body 

 both cells and toxins must therefore possess certain reciprocal 

 configurations. It has been suggested further that these side 

 groups are concerned in all the actions of the cells and that it 

 is through them, for example, that the latter absorb their nec- 

 essary nutriment and elaborate new structures from it. Some 

 of the side chains may be constructed to combine with fats, 

 some with carbohydrates and some with proteins, but in the 

 presence of toxins or bacteria with the right kind of side chains 

 combination with these may take place instead. Many of 

 these combinations, perhaps all, take place not directly, but 

 indirectly, through the presence of an intermediary body or 

 group which itself must possess two linking complexes or 

 groups with proper configurations. 



To describe these various groups certain special names have 

 been suggested. Immune body is the specific substance 

 formed in the immunizing process against cells and is known 

 also by several other names, among which amboceptor and in- 

 termediary body are the most commonly used. The comple- 

 ment,, addiment or alexin is the ferment-like body found in 

 normal fresh serum, and which added to the immune body 

 makes up the real cytotoxin. It is not specific and, as inti- 

 mated above, is sensitive to heat, and also to light and air 

 (oxygen). The various groups of the large cell complex, 

 whether of a body cell or of a bacterium, which have the power 

 of uniting with other groups are called receptors. The part 

 of the receptor which is free to combine with a food molecule 

 or analogous substance is called its haptophorous group. Ehr- 

 lich pictures the part played by the immune body and the com- 

 plement in this way. Assuming that a bacterial cell enters a 



