TRANSPLANTATIONS 39 



of the lymph vessels and they collected at the periphery of the center, or they 

 filled the center diffusely; moreover, lymphocytes and also some connective 

 tissue cells surrounded some acini. The central portion of the parathyroid was 

 necrotic and in process of organization. Mitoses were seen in both thyroid and 

 parathyroid. 



In series A, between the 10th and 15th day, the thyroid transplant had dis- 

 appeared, only fibrous tissue with some lymphocytes was observed in a number 

 of cases. In other experiments there were some isolated acini or groups of 

 acini embedded in masses of lymphocytes, which had accumulated and which 

 gave to the transplant almost the appearance of a lymph gland. Lymphocytes 

 could be seen penetrating between and into certain acini and destroying them. 

 The center of the transplant was densely fibrous and blood vessels were here 

 less conspicuous. As a rule, the thyroid ring, if present at all, was incomplete. 

 After 16 and 17 days, variable amounts of thyroid tissue were found pre- 

 served; if the amount was small, the colloid was usually lost. Fibrous bands 

 separated acini or bundles of acini and lymphocytes separated acini in certain 

 areas; the center of the transplant and the lymph vessels were filled with 

 lymphocytes. There was some indication also in this series that the homoio- 

 reaction was especially marked after transplantation in certain strains of rats. 



Series B differed from series A in that, in the former, the reactions were 

 on the average slightly less severe up to about 30 days after transplantation, 

 but from then on, a diminution in the intensity of the lymphocytic reaction 

 and in the destruction of thyroid issue set in, which was quite noticeable be- 

 tween the 40th and 85th days. While the lymphocytic reaction appeared some- 

 what later in series B, a marked lymphocytic infiltration did occur, and fibrous 

 bands surrounded the acini during the earlier periods. In both series, in ex- 

 ceptional cases, the grafts showed the character of typical syngenesiotrans- 

 plants, in which, instead of dense fibrous tissue, there was loose connective 

 tissue with blood vessels in the center ; here lymphocytes had accumulated as 

 well as in the periphery of the graft and they penetrated also between the 

 acini. But in other instances there was, in these cases, an intense destruction 

 of the thyroid by lymphocytes and connective tissue. 



In series C, a complete or almost complete destruction of thyroid and para- 

 thyroid had occurred at about 20 days after transplantation, the reaction being 

 very severe, in accordance with the greater difference between the individuality 

 differentials of host and donor. There are, then, indications that the intensity 

 of the reactions against transplanted thyroid varies in accordance with the 

 relationship between host and transplant. 



In homoiogenous transplantations of the thyroid gland in the guinea pig, 

 which were carried out with Hesselberg, the results were very similar to those 

 obtained in rats. Yet some differences between autogenous and homoiogenous 

 transplantations are brought out perhaps more clearly in the former than in the 

 latter species. In a first period, lasting about four to five days and representing 

 the earliest reaction to the injury, there is no marked difference between 

 transplantation of autogenous and homoiogenous thyroid. During this interval 

 the first mitoses appear and at the end of it some new acini may be produced. 



