REPRODUCTION 



1023 



Transplantation of Tissues. Besides the growth and regeneration 

 of tissues or organs, the simple displacement of them from their 

 normal situation and their implantation in a new environment have 

 been studied. Normally, a migration of tissue elem3nts is only 

 witnessed in the adult in the case of cells moving with the circulating 

 liquids, or endowed with the power of amoeboid movement. Under 

 pathological conditions fragments of tissue, such as tumour cells, 

 may be carried by the blood or lymph to distant parts, and, settling 

 there, may undergo development (forming metastases). In the 

 embryo the slow migration of tissue elements is a process which 

 is responsible for some of the anatomical peculiarities of the adult. 

 The migration of the ovum from the ovary is the starting-point of 

 the process of reproduction. The artificial displacement of tissues 

 within the body of one and the same animal (auto- or homo-trans- 



FIG. 446. METHOD OF TRANSPLANTATION (OF BOTH KIDNEYS) IN MASS. 

 (AFTER GUTHRIE.) 



Segments of the inferior vena cava and abdominal aorta are removed with the 

 kidneys and renal vessels, and interposed in the course of the vena cava and aorta 

 of another animal, according to the method of Carrel and Guthrie. 



plantation, or graft), or from one animal to another of the same 

 species (iso-transplantation, or graft) has been successfully accom- 

 plished in many cases. But hetero-transplantation, or grafting 

 between animals of different species, is in general not permanently 

 successful, the graft undergoing cytolysis (p. 29) in the alien en- 

 vironment. 



Transplantation, or engrafting, may be done either with or without 

 anastomosis of bloodvessels. In the second method a portion of 

 tissue, usually small, or a small organ, is simply inserted in its new 

 situation without provision for the immediate establishment of a 

 circulation in it. Strips of cuticle may easily be grafted in this way 

 to restore deficiencies in the skin after burns or extensive opera- 

 tions. The ovary can also be grafted by simple implantation with 

 success, Guthrie has thus shown that hens whose ovaries have been 



