GRAFTING 415 



for the transplanted tissue. Thus, if a fragment of the 

 thyroid is transplanted and the greater part permitted 

 to remain in its normal position, the graft is apt to 

 suffer absorption apparently because it is not physio- 

 logically necessary. The absence of the physiological 

 necessity probably explains many failures in trans- 

 planting thyroid tissue. 



Knauer and Grigorieff performed many experiments 

 by transplanting the ovaries of rabbits to new situations 

 in the abdominal cavity and found that though the 

 central portions of the transplanted organs usually 

 underwent necrosis and were replaced by fibro-connect- 

 ive tissue, the superficial layer containing the follicles 

 and ovules escaped destruction so that the function of 

 ovulation was not affected. Three of the rabbits whose 

 ovaries had thus been transplanted subsequently became 

 pregnant, so that it appears that the ovules liberated into 

 the abdominal cavity found their way to the Fallopian 

 tubes and uterus. 



Morris, in removing the ovaries and tubes from a human 

 patient, grafted a portion of one of the removed ovaries 

 upon the stump of one of the tubes. This graft took, 

 and the patient later became pregnant. 



Skin grafting has become a frequent and useful surgi- 

 cal method for facilitating the restoration of the dermal 

 covering in extensive ulcer ations such as follow super- 

 ficial burns, etc. The grafts can be taken from any 

 part of the patient's body and need not be large; in fact, 

 a number of small grafts seem quite as useful, if not 

 more so, than the transplantation of considerable por- 

 tions of skin. In these cases, the superficial layers of 

 the epiderm are useless as they have no longer sufficient 

 vitality to permit them to multiply; any transplanted 

 subcutaneous tissue is likewise useless, as it is absorbed. 

 The essential portion comprises the rete mucosum whose 

 cells have great tenacity of life they may be kept 

 alive in salt solution for ten days or two weeks become 

 amoeboid in the new environment, and by their multi- 



