TRANSPLANTATIONS 43 



planted fat tissue and replacement of the latter by fibrous tissue. Variable 

 amounts of fat tissue could remain preserved, but it might be invaded by 

 epithelioid and giant cells. Lymphocytic infiltration was usually marked in the 

 fibrous tissue around the cartilage as well as around the blood vessels which 

 supplied the fat tissue with blood, and also around the bone, but at other times 

 the infiltration was moderate. In one transplant, even remnants of striated 

 muscle tissue with nuclear chains were found. On the whole, the connective 

 tissue and lymphocytic reaction against the transplant was considerable in 

 series C, and more intense than in series A and B. Likewise, the bone marrow 

 became more rapidly and more completely necrotic and it was more exten- 

 sively replaced by fibrillar connective tissue than it was in the first two series. 

 In series A and B, the necrosis of the fat tissue was less marked than in series 

 C or it was lacking altogether, and there was often only localized ingrowth of 

 connective tissue into the fat tissue, together with a moderate invasion by 

 lymphocytes, which had a tendency to collect around the perichondrium. 



As to the time relations in these reactions, they were about as follows : In the 

 first three days after transplantation there was noticeable a movement of some 

 polymorphonuclear leucocytes in the fat tissue, in the direction towards the 

 cartilage ; these cells disappeared in the following days. Between the 6th and 

 8th day, a new formation of cartilage could set in and a slight infiltration with 

 lymphocytes, varying in strength in different specimens, took place. The re- 

 action against the transplanted tissue usually was quite distinct on the 10th 

 day after transplantation and the maximum could be reached between the 20th 

 and 30th day. At this time, the average grade in series A was about 2— and 

 in series B it was intermediate between 2— and 2. Between the 30th and 85th 

 day a decrease in the average severity of the lymphocytic infiltration could 

 occur, while the connective tissue reaction remained in a quiescent state. In 

 some instances, at late stages the transplant even resembled an autotransplant, 

 perhaps on account of an adaptation of the host to the originally strange tissue, 

 a condition possibly akin to a state of active immunity. 



In general there was, in the various experiments, a parallelism in the grades 

 of thyroid and cartilage-fat transplants. In rats, in which the homoiogenous 

 reaction was weak or lacking altogether in thyroid transplants, it was also as 

 a rule lacking or weak in cartilage-fat transplants ; but the destruction of the 

 tissue by lymphocytes and connective tissue was, on the whole, much greater 

 in the thyroid than in the cartilage; however, there were some instances in 

 which the thyroid transplant was so markedly invaded by lymphocytes that it 

 almost resembled a lymph gland, and then the cartilage-fat transplant likewise 

 was severely infiltrated. On the whole, then, the principles which applied to 

 the relationship between the individuality differentials of host and transplant 

 and the reactions towards the transplanted tissues were about the same in the 

 case of thyroid and cartilage-fat tissue. 



6. Autogenous and homoiogenous transplantations in the guinea pig, of 

 cartilage-fat tissue with the associated tissues, are very similar to the corres- 

 ponding conditions in the rat. Again, in the first stages following transplanta- 

 tion there may be in both kinds of transplants, some polymorphonuclear leu- 



