TRANSPLANTATIONS 51 



infiltration of the homoiogenous tissue in the back of the abdominal wall than 

 in the ear. In the autogenous transplants there were occasional lymphocytes 

 around the tubules or in the capillaries of glomeruli, especially in places where 

 the connective tissue was increased around the tubules, but often they were 

 entirely absent, while they were very prominent in homoiogenous pieces, es- 

 pecially in those transplanted into the abdominal wall. 



The lymphocytic infiltration is distinct after nine days in homoiotransplants, 

 after which period it increases gradually — this applies also to transplants in 

 the ear, although here it is less prominent. Lymphocytes collect around the 

 kidney transplant and penetrate into the lumen of the tubules as well as into 

 the glomeruli, isolating and helping to destroy and replace the tubules. The 

 destruction of tubules by these cells can be seen at ten days after transplanta- 

 tion and it persists from then on. In the central necrotic or organized area they 

 are present in smaller numbers. However, the intensity of the lymphocytic re- 

 action varies in different homoiotransplants ; it apparently is not prevented nor 

 even noticeably diminished by a loss of even as much as one-half of the weight 

 of the host. This reaction was similar in strength in thyroid and in kidney ; in 

 both these organs, after homoiotransplantation, it became noticeable at about 

 the same time and gradually progressed. If a bacterial infection takes place, 

 the tissue at some distance from the place of infection may remain preserved, 

 and the infection does not call forth a lymphocytic reaction in autogenous 

 transplants nor does it noticeably increase it in the case of homoiotransplants ; 

 but ordinarily already the lymphocytic reaction is marked around and in 

 homoiotransplanted kidney. As we have stated, in homoiotransplanted tissue 

 of the mouse it seems that bacterial infection may increase the intensity of 

 the lymphocytic reaction. 



While the degree of compatibility between the individuality differentials of 

 host and transplant largely determines the reaction on the part of the lympho- 

 cytes, the less specific factors of injury sustained by the transplants during and 

 following the transplantation, the unfavorable conditions in the transplant, 

 caused by its strange situation, and the difficulty of entering into normal rela- 

 tions with the new tissues surrounding it are, to a greater extent, responsible 

 for the activity of the fibroblasts and the production of fibrous tissue. The 

 organismal differentials are of less significance in these latter changes, al- 

 though they are still important. In both autogenous and homoiogenous tissues 

 the connective tissue grows between the tubules and glomeruli of the peripheral 

 zone and progresses towards the central necrotic material. However, a larger 

 number of fibroblasts seem to grow into the homoiotransplants; this is es- 

 pecially clear following the first two weeks, when the injury due to the opera- 

 tion has in great part subsided. In the autogenous transplants the closely ap- 

 proximated tubules are arranged in lobules and it is the lobules which are 

 separated by connective tissue, whereas, in the homoiotransplants the individ- 

 ual tubules are separated by connective tissue; but strands of connective tissue 

 may surround some individual tubules also in autotransplants. Through the 

 exertion of pressure by this tissue the lumen of the central tubules is obliter- 

 ated or shrunken. But in addition there may be atrophy as a result of insuffi- 



