68 M. F. GUYER AND E. A, SMITH 



I 



that for some bacteria, at least, the bone-marrow, spleen, and 

 lymph nodules pjroduee the antibodies. 



Although presumably distinct from one another, the various 

 classes of antibodies seem to have many points of similarity, 

 as, for instance, their method of origin, their reaction to heat, 

 and their mode of operation. Chemically their natures are still 

 unknown. Many of them seem to function through the combined 

 action of at least two separate constituents. In some instances 

 perhaps more constituents are involved. One of the compo- 

 nents developed in response to injected foreign substances, such 

 as bacteria, cells, dissolved proteins, various ferments, toxins, 

 and venoms, though variously named by different workers, is 

 commonly called the immune body or amboceptor. The other, 

 an ingredient of normal serum, is termed the coviplement. 

 Whether a single complement acts alone or a series of comple- 

 ments operate in conjunction with the amboceptor is a matter of 

 dispute. Complement, in general, decomposes readily upon 

 warming much above blood heat or spontaneously upon stand- 

 ing. It seems much less stable in every respect than the ambo- 

 ceptor, though the latter is the specific constituent developed 

 through the introduction of an antigen. 



The union of such foreign substances as amboceptors with a 

 living cell is possible, according to Ehrlich's conception, be- 

 cause of the existence of a series of secondary chemical con- 

 stituents or groups attached to the main living molecules of 

 that cell. To these he has given the name of receptors. Since 

 this term is in common usage, it is perhaps well to retain it 

 until a better one for the existing condition is forthcoming, 

 even though all workers would not subscribe to the implica- 

 tions it suggests. While receptors are supposed by Ehrlich to 

 have a great variety of functions, he regards that of assimila- 

 tion as of particular importance. To combine with these re- 

 ceptors any given substance (e.g., amboceptors) must possess, 

 supposedly, very definite constitutional or configurational rela- 

 tions to the receptors in question. 



One vie^\^ looks upon the complement present in all serum as a 

 sort of a ferment possessing digestive properties. It is power- 



