70 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



Fibrous tissue grew around and into the transplant. Also, cartilage and fat 

 tissue were necrotic, but the peripheral portions of these pieces had been 

 fixed as a result of the boiling. Connective tissue and small vacuolated cells 

 grew into the fat tissue, but the lymphocytic reaction was lacking. After 20 

 days, the results were similar. In the thyroid, some balls of hard colloid, sur- 

 rounded by some giant cells and fibrous tissue, were seen. At this time also, 

 connective tissue grew into thyroid and into necrotic fat tissue, in which, in 

 addition, small vacuolated and epithelioid cells were seen. A few polymorpho- 

 nuclear leucocytes were likewise noted in the connective tissue, but a typical 

 lymphocytic reaction was absent, and the homoiogenous fat tissue did not 

 attract polymorphonuclear leucocytes. These experiments confirm, then, the 

 conclusion that in general, if we except reactions of a non-specific nature, such 

 as the ones elicited by certain dead foreign bodies, only living tissue calls forth 

 the lymphocytic reaction which is characteristic of transplants possessing 

 homoiogenous individuality differentials. 



5. The autogenous tissue regulators. In the normal organism the various 

 types of cells have inherited those modes of interaction with other cells and 

 intercellular substances of different kinds, by means of which the mutual cell 

 and tissue relations are safeguarded. Hence, whenever the various types of 

 transplanted tissues possess the same autogenous chemical characteristics of 

 the individuality differential as the host, they tend to interact with the host 

 tissues as if they were a normal constituent of the host, even if at first a dis- 

 organization has taken place as the result of temporary accidental conditions. 

 The disappearance at later dates of factors disturbing the normal tissue rela- 

 tions directly following autogenous transplantation of thyroid, cartilage, fat 

 tissue and uterus, indicates the presence of autogenous regulators. However, 

 not in all organs do such regulators suffice to overcome the abnormalities 

 brought about by the operation ; for instance, in the transplants of kidney a 

 complete normality in the structure of the transplant does not need to be 

 achieved. A perfectly closed epithelial layer may survive permanently after 

 autotransplantation, but incompletely closed epithelial structures, such as 

 kidney tubules which have been cut at one end, and especially the more differ- 

 entiated convoluted tubules or epidermal cysts which are interrupted by hairs, 

 are at a disadvantage and may die even after autogenous transplantation. 



After homoiogenous transplantation of various tissues and organs in a 

 number of species, the interaction of disharmonious individuality differentials 

 leads to abnormal relations between host cells and transplanted tissue. The 

 homoiogenous substances given off by the transplants stimulate and attract 

 lymphocytes and connective tissue cells, with graded intensities which exceed 

 the threshold of normality, and in addition, homoiogenous substances of the 

 host may injure directly the homoiogenous tissues, whose relation to stroma 

 cells and blood vessels and to lymphocytes in the adjoining areas of the host is 

 thus altered. In the end, in the large majority of cases the transplanted tissue 

 is either destroyed or at least its normal structure and relations to the neigh- 

 boring tissues are not completely re-established. 



Regeneration may also be considered as a regulatory process in the relations 



