TRANSPLANTATION AND INDIVIDUALITY. 163 



organism and subsequently function as such, substances are given 

 off by the tissues and organs which act upon adjoining or distant 

 parts of the body and thus bring about a correlation of functions 

 which makes possible the orderly development and maintenance 

 of the organism. Some of these substances still preserve the 

 individuality and species differential. We may, therefore, con- 

 clude that not only cells, but also substances given off by cells 

 may still have the individuality or species differential. This 

 applies to some of the contact substances which we have postu- 

 lated. They may have the individuality differential. In most 

 substances, however, the presence of an individuality differential 

 cannot be demonstrated, but merely the existence of a species dif- 

 ferential. Of especial interest among these are certain sub- 

 stances which make use of this species differential in their func- 

 tion and which are therefore most effective if they interact with 

 other substances having the same species differential or rather 

 a supplementary species differential adapted to the first differ- 

 ential. Such substances I have called " specifically adapted sub- 

 stances.'' To this group of specifically adapted substances belong, 

 as I found in my earlier work, substances which are present in 

 the tissues and erythrocytes and which interact with a constituent 

 of the circulating bodyfluid in order to accelerate the clotting of 

 the blood and lymph. These substances I have called tissue 

 coagulins. They seem to be id~entical with the thrombokinases. 

 The species differential fulfills in this case a definite and im- 

 portant function. Subsequently Hedin discovered in the gastric 

 juice a substance inhibiting the milk coagulating enzyme. Both 

 these substances interact with the species differential. More re- 

 cently Dr. Frank Lillie found a specificially adapted relation be- 

 tween a constituent of the egg, an agglutinin, and the spermatozoa 

 of the same species. In this case, however, the common species 

 differential functions in substances belonging to two different 

 individuals, while in the former cases the interaction occurs in 

 substances of the same individual. On the other hand a large 

 number of important substances which have the function to cor- 

 relate and unify the action of various organs, particularly certain 

 growth substances and the common hormones are not only not 



