42 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



of cartilage around the necrotic area, and in some instances the newly- formed 

 cartilage may even infiltrate and take the place of the necrotic part. Corre- 

 spondingly, central necrosis and solution processes may be found even in 

 the normal, not transplanted xiphoid cartilage, in places where it is thick and 

 where the central parts are therefore not well nourished. Transplanted fat 

 tissue remains normal, but occasionally necrotic areas are found in it, pre- 

 sumably as the result of injury inflicted upon it during the transplantation ; 

 there may be at first very slight collections of lymphocytes, due probably 

 to the presence of necrotic areas or to other accidental alterations of the fat 

 tissue, but these disappear somewhat later. 



5. Homoiogenous transplantation in the rat of cartilage and fat tissue pro- 

 duces the changes characteristic of homoiogenous individuality differentials. 

 The same three series of transplantations were made in the rat with cartilage, 

 bone and fat tissue as with thyroid. With thyroid, there was a grading of the 

 intensity of the reaction, corresponding to the average degree of similarity or 

 lack of similarity of the individuality differentials in these series. Upon this 

 condition depended the amount of tissue destroyed and replaced by fibrous 

 tissue and the intensity of the lymphocytic reaction. If we compare with these 

 gradations in thyroid, the gradations in cartilage, bone and fat tissue trans- 

 plants, we find in principle, in both kinds of grafts, the same condition, except 

 that the differences in the power of resistance of different tissues caused some 

 differences in the mode of reaction and in the absolute grades given. The 

 greater portion of the cartilage could remain alive permanently in all three 

 series of homoiotransplantations, but the fate of the fat tissue, epiphyseal 

 cartilage, bone and bone marrow, and the frequency and character of the 

 regenerative processes around necrotic parts of the cartilage served as indica- 

 tors of the severity of the reaction and of the degree of compatibility of the 

 individuality differentials of host and transplant. 



Even in series C, in which host and donor of the transplant were least nearly 

 related, the cartilage remained alive, and if there was localized necrosis a 

 regeneration of perichondrial cartilage could take place, although this did 

 perhaps not occur as regularly as in series A and B, and in some cases it led 

 to the formation of a myxoid tissue instead of cartilage ; this occurred if the 

 intercellular cartilage substance was dissolved, while the cartilage cells re- 

 mained alive. Evidently the development of toxic substances could inhibit the 

 regeneration of cartilage. The epiphyseal cartilage and the transplanted bone 

 were completely or almost completely necrotic in this series. However, there is 

 some difficulty in the determination of the degree of necrosis of bone. If we 

 adopt the condition of the bone cells as a criterion of the life or death of this 

 tissue, then we encounter the difficulty that many of the apparently preserved 

 and living bone cells may in reality be connective tissue cells, that had moved 

 into the bone from the outside, in particular, from a zone of epithelioid cells 

 surrounding the bone-cartilage border and perhaps representing merely fibro- 

 blasts, which, under the influence of bone tissue, assumed the character of 

 epithelioid cells. But ordinary connective tissue cells may also invade and 

 replace necrotic bone and cartilage. There was extensive necrosis in the trans- 



