SENSITIZING ANTIBODIES 203 



over, are not of the relatively simple soluble character of the toxins, 

 but are intrinsic portions of complex albuminous molecules, com- 

 parable to and often identical with the true nutritive substances. 

 For these reasons Ehrlich believes that the cell-receptors for the 

 various substances which give rise to agglutinins and precipitins 

 are neither of the simple structure of the toxin receptor, nor of the 

 double-haptophore nature of the bacteriolytic receptors, but contain 

 a single haptophore group for the anchorage of the ingested material 

 and at the same time a constantly attached zymophore group or 

 ferment by means of which the anchored substance is transformed 

 preparatory to its absorption by the cell protoplasm. For the sake 

 of clearness, this form of receptor may be compared to a bacteriolytic 

 or hemolytic amboceptor with a permanently attached and insepa- 

 rable complement. 



Three forms of receptors, then, are proposed by Ehrlich in ex- 

 planation of all known varieties of antibodies. The first, the sim- 

 plest side chains of the body cells, he calls "receptors or haptines 

 of the first order. ' ' These, overproduced and cast off, constitute the 

 antitoxin and antiferments. Next "haptines of the second order" 

 are the receptors planned both for the anchorage and further diges- 

 tion of antigens. These, free in the circulation, are the precipitins 

 and agglutinins. "Haptines or receptors of the third order" are 

 merely able to anchor a suitable substance, but exert no further 

 action upon it until re-enforced by the complement normally present 

 in the serum. These, free in the circulation, with a chemical group 

 having avidity for the antigen, and another complementophile group, 

 are the amboceptors or immune bodies of bacteriolytic, cytolytic, 

 and hemolytic sera. 



We cannot, in a general work of this kind, go into a detailed 

 discussion of the many complex problems involved in regard to 

 the structure of antibodies. Again we will refer the reader to the 

 larger works on this subject. It is our opinion, however, that the 

 above views of Ehrlich can no longer be maintained in the light 

 of present knowledge. 



Bordet, 44 points out that the conception of Ehrlich rests upon 

 the basis of a number of undemonstrated hypotheses. He asserts, 

 and with justice, that it has never been shown beyond question that 



44 Bordet, Kesume of Immunity in Bordet 's ' i Studies in Immunity, ' ' transl. by 

 Gay, Wiley & Sons, 1909, 



