REACTIONS AGAINST INDIVIDUALITY DIFFERENTIALS 71 



between tissues and it is based essentially on inherited properties of the tissues. 

 These inherited characteristics assert themselves in all instances, irrespective 

 of the autogenous or homoiogenous state of the transplants. In certain tissues, 

 which possess great resistance to injurious conditions and in which the re- 

 generative momentum is very strong, regenerative processes may take place 

 in a homoiogenous medium, but the homoiogenous relationship always tends 

 to act as an injurious factor, preventing or at least inhibiting regenerative 

 activities. 



There enter, then, at least two factors in the creation and maintenance of the 

 autogenous tissue equilibrium, namely (1) the individuality differentials, 

 which diffuse from the tissues into the surrounding bodyfluids and which 

 are present also in the blood; (2) other factors inherent in the tissues, which 

 assert themselves under certain conditions, as, for instance during regenera- 

 tion. There exists the probability that the autogenous individuality differentials 

 as such function as these tissue equilibrizing substances ; but it is also con- 

 ceivable that there may exist special autogenous tissue-regulating substances, 

 which possess a chemical group characteristic of the individuality differential 

 of the host, or that there may be separate autogenous substances devoid of 

 the individuality differential but which could induce the tissues to react in the 

 normal manner only in an autogenous medium. However, the first interpreta- 

 tion seems to be the simpler and more ^probable one. Just as the homoio- 

 genous individuality differential exerts abnormal effects on various types of 

 cells, so the autogenous individuality differential may be expected to exert 

 the opposite functions, which in contrast to the homoiogenous substances 

 bring about and maintain a normal relation between the various tissues. These 

 substances, acting on adjoining tissues as contact substances which latter in a 

 wider sense may be included among the hormones, although not usually thus 

 classified, and acting also on distant tissues as hormones in the usual mean- 

 ing of this term, would thus possess a very important function in making 

 possible the harmonious interaction of the many constituent parts of the in- 

 dividual organism; however, they would be supported in this task by other 

 typical hormones produced in distant organs, which do not necessarily possess 

 the individuality differential, and also by specific elements of the nervous 

 system. 



