52 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



cient nourishment. The mechanism underlying these relations of the connective 

 tissue to various types or degrees of injury of the parenchyma is, as yet, very 

 little understood. Stereotropic reactions, movements in contact with strange 

 foreign bodies, perhaps chemotropic activity elicited by necrotic tissue, as well 

 as other altered relations between the more specific parenchymatous tissue and 

 the surrounding stroma, may form the stimulus for both movements and in- 

 crease in size and multiplication of cells in the surrounding connective tissue. 

 It is these factors which may ultimately lead also to the destruction of auto- 

 genous skin cysts in the guinea pig, which form after subcutaneous trans- 

 plantation of epidermis with the underlying connective tissue. Here the sur- 

 rounding connective tissue may grow stereotropically along the hairs of the 

 skin into the interior of the cyst, where it separates and surrounds the keratin 

 lamellae. Thus after some time the host connective tissue may bring about the 

 destruction of autogenous subcutaneous skin transplants ; but in addition there 

 develop specific lymphocytic reactions around homoiogenous skin grafts. 



The size and character of the central necrotic area in transplanted kidney 

 varies in different animals ; the organizing fibroblasts grow first between and 

 along the necrotic tubules and then into the tubules. As the result of the organi- 

 zation of the fibroblasts the necrotic material becomes hyaline ; in addiion, the 

 latter is taken up by phagocytes, which thus aid in its removal. On the whole, 

 on account of the relative hardness of the necrotic kidney tissue, the organiza- 

 tion progresses slowly and with unequal rapidity in different hosts ; it may re- 

 quire 20 days or even longer for this process to be completed. Following or- 

 ganization of the autotransplanted thyroid, as we have stated, the central 

 necrotic part after some time becomes cellular and small in size, but the 

 homoiotransplanted thyroid is fibrous-hyaline and large. However, in the kid- 

 ney there is no marked difference between the condition of the central parts in 

 autogenous and homoiogenous transplants, because in both, the necrotic kid- 

 ney tissue is resistant to the action of the organizing host cells. The principal 

 difference between the two types of kidney transplants consists in the number 

 of lymphocytes and of fibroblasts and in the amount of connective tissue in the 

 peripheral living area. 



The tubules in the transplanted kidney are simple and similar to the collect- 

 ing tubules. The glomeruli are small and tend to be hyaline. There are frequent 

 mitoses in the tubules between five and seven days ; at nine days a mitosis was 

 found in a glomerulus. From the 7th or 8th day on, a decrease in their num- 

 ber occurs, but they are found even after 27 days, although not after 30 days, 

 in both autogenous and homoiogenous transplants. The mitotic activity may, 

 at least for some time, be as great in the latter as in the former, or even greater. 

 As a result of the transplantation a chain of changes is initiated in the trans- 

 plant, irrespective of the character of the individuality differentials, and these 

 changes lead to mitotic cell proliferation; gradually this reaction curve de- 

 clines, and at last a new equilibrium is reached in which cell proliferation 

 ceases, although the original normal condition of the transplant has not been 

 restored. These curves of changes are similar in thyroid, kidney and uterus 

 transplants, although some differences exist. It is possible that in homoio- 



