240 INFECTION AND IMMUNITY 



chains of the body cells, he calls " receptors or haptines of the first order." 

 These, overproduced and cast off, constitute the antitoxin and antifer- 

 ments. Next " haptines of the second order" are the receptors planned 

 both for the anchorage and further digestion 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 sub- 

 stance, but exert no further action upon it until re-enforced by the com- 

 plement 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. (See Fig. 62.) 



It is plain that all these receptors while still parts of their respec- 

 tive cells, serve by their chemical affinity to attract and hold the foreign 

 substances injected; freely circulating, on the other hand, they serve 

 in preventing these substances from reaching the cells. As Behring 

 has aptly expressed it, the very elements which situated in the animal 

 cells render the body susceptible to toxic substances serve to protect 

 when circulating freely in the blood. 



Bordet, 1 at present the strongest antagonist of Ehrlich's point of 

 view, claims 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 the antibodies, 

 free in the serum, are identical with the receptors of the body cells 

 upon which the antigen originally acts. 



In regard to agglutinins, Ehrlich, as we have seen, believes that it is 

 the agglutinin itself which, first uniting with its antigen by its hap- 

 tophore group, then causes clumping by its zymophore group. Now, 

 as a matter of fact, Bordet 2 has shown that it is not the agglutinin itself 

 which agglutinates, but that agglutinin with its antigen forms a com- 

 plex which is then agglutinable by the salt present in the solution. This 

 conclusion seems borne out by the later work of Gengou, 3 Landsteiner 

 and Jagic, 4 and others, who have shown that bacteria which have ab- 

 sorbed other substances, such as uranium compounds, colloidal silicic 

 acid, etc., are subsequently agglutinable by salts. In consequence, 

 from these and other observations, Bordet concludes that it is neither 

 necessary nor accurate for the explanation of these phenomena, to 



1 Bordet, Resume of Immunity in Bordet's " Studies in Immunity," transl. by Gay, 

 Wiley & Sons, 1909. 



2 Bordei. Ann. de 1'inst. Pasteur, 1899. s Gengou, Annal. Past., 1904. 

 4 Landsfeiner und Jagic. Wien. klin. Woch., iii, 1904. 



