K. LANDSTEINER 903 



and these lysins can be absorbed by the A cells. The results disclose a similarity of 

 the agglutinogen of group A and Forssman's antigen; however, the two substances 

 are not the same since, aside from other reasons, the experiments described did not 

 succeed regularly but only with certain immune sera. 



INDIVIDUAL DIFFERENCES OF ANIMAL BLOOD 



As Stated already, individual variations in animal blood were first shown with the 

 aid of isoantibodies formed by the injection of blood into other individuals of the same 

 species. This method, used for goat blood by Ehrlich and Morgenroth, was applied 

 to other animals such as dogs,' cattle, chickens, cats. It was believed that such re- 

 sults could be obtained only with isoantibodies. But later work brought out the 

 fact that like reactions may be exhibited by immune sera derived from a foreign 

 species.^ Indeed, for human blood this had already been observed. Also normal iso- 

 agglutinins and isolysins occur in animals — for instance, in the blood of cattle, sheep, 

 chickens, cats, horses, and pigs. For several species — mice, rabbits, monkeys — no 

 satisfactory evidence was obtained of the existence of individual blood differences. 



In some species groupings were found analogous to those of human blood but not 

 quite as regular.^ A direct relation of the serological findings to racial differences does 

 not seem to exist; there is only an unequal frequency of the agglutinogens among 

 various races^ (see p. 907). 



The experiments of Todd and White^ with immune isolysins for cattle blood are 

 remarkable in view of the great number of individual differences which they observed. 

 Similar results were obtained with chicken blood. ^ One may be inclined to correlate 

 these findings with the individual varieties which were established in the studies on 

 transplantation of normal tissues and tumors (cf. L. Loeb). 



CHEMICAL NATURE OF THE ISOAGGLUTINOGENS 



The chemical nature of the isoagglutinogens of red cells in general was a matter 

 of much discussion. Recent investigations indicate that these antigens probably con- 

 sist of proteins combined with other substances which determine at least in part the 

 specificity of the whole complex (cf. Landsteiner and van der Scheer). It was first 

 shown for the heterogenetic antigen of Forssman that by extraction with alcohol a 

 material free from protein could be separated which reacts specifically with hetero- 

 genetic antibodies in vitro but has no antigenic activity unless it is injected along with 

 protein. An active fraction obtained from the alcoholic extract was found to contain 

 carbohydrates and fatty acids. Similar observations on the extraction of specific 



'von Dungern, E., and Hirschfeld, L.: loc. cit. 



^ Landsteiner, K., and van der Scheer, J.: /. Immunol., 9, 213. 1924; Landsteiner, K., and Miller, 

 C. P.: Proc. Soc. Exper. Biol, b' Med., 22, 100. 1924. Cf. the interesting observation of sheep blood 

 lacking Forssman's antigen (Mutermilch, S.: Ann. de Vlnst. Pasteur, 38, 1002. 1924). 



3 Concerning their possible relation to human isoagglutination see Amzel, R., Halber, W., and 

 Hirszfeld, L.: Ztschr.f. Immunitdlsforsch. u. exper. Tlierap., 42, 369. 1925. Cf. Soc. Biol., 94, 204. 

 1926; Witebsky, E.: Ztschr.f. Immunitdtsforsch. u. exper. Therap., 49, i, 517. 1926-27. 



-• Bialosuknia, W., and Kaczkowski, B.: /. Immunol., 9, 593. 1924. 



5 Todd, C. H., and White, R. G.: /. II yg., 10, 1S5. 1910. 



^Landsteiner, K., and Miller, C. P.: loc. cit. 



