100 COLLECTED STUDIES IN IMMUNITY. 



tions do not correspond to two different single immune bodies, but each 

 fraction includes several, perhaps an entire host of immune bodies. 



The experiments also lead to conclusions of considerable impor- 

 tance in another direction, namely, as affecting our conception of 

 cellular specificity and of the specificity of reaction products. Here- 

 tofore it has been held that the injection of blood of species a results 

 in a specific immune serum, i.e. one acting only on a; and even 

 Metchnikoff l has recently expressed this view. We had already 

 become acquainted with certain exceptions to this principle. The 

 isolysin, for example, produced by injecting goats with goat blood, 

 also dissolves sheep blood; and, vice versa, the immune body of 

 goats which have been injected with sheep blood acts also as an 

 isolysin. At that time we emphasized that these results are onl]" 

 to be explained by assuming that certain types of receptors are com- 

 mon to both species of blood. The same holds true in the case 

 under discussion, von Dungern 2 has come to the same conclusion 

 as a result of his experiments. He found that the immune body 

 produced by injection of ciliated epithelium acts also on the blood- 

 cells of the same species, and that conversely the haemolytic immune 

 body produced by injection of blood-cells is partially bound by 

 ciliated epithelium. 



All these circumstances indicate that we must not regard the spe- 

 cificity of the immune bodies from the conception of specificity employed 

 in systematic zoology and botany. The immune sera, as we have often 

 mentioned, are not of simple Unitarian nature, but consist of a series 

 of single immune bodies whose cytophile haptophore groups cor- 

 respond to the receptors of the exciting cells. Hence such an immune 

 serum will be able to affect all such elements which possess any one of 

 the receptors uihose type is common to those elements and the original 

 cell "a." The influence exerted by the immune serum will be power- 

 ful in proportion to the extent of this correspondence of receptors. 

 Now we have reason to believe (cf. Ehrlich's deductions, 1. c., and 

 Weigert's in Lubarsch-Ostertag's Ergebnisse der Pathologic, 1887, p. 

 141) that certain receptors are very widely distributed among various 

 animal species. Thus the blood-cells of a large number of species 

 possess receptors fitting ricin, abrin, crotin, and tctanoli/sin, and gan- 

 glion cells of the most divergent animals possess receptors for tetano- 



1 Revue gi-rn'rale des sciences, 1901, No. 1. 



2 See page 47. 



