BLOOD VESSEL ANASTOMOSIS 167 



skin junctions, but in some cases there may be, in addition, connections 

 through large omental blood vessels. To the peritoneal-skin union there is 

 usually added, in parabiosis, a union by skin flaps, which increases the size 

 of the area of vascular connection between the two animals. Characteristic 

 of parabiosis is, then, the combined action of two systems of bodyfluids and 

 of two kinds of individuality differentials in the same individual; however, 

 there is a great quantitative predominance of the animal's own constituents 

 over the strange ones carried to him from his partner. There are some 

 related parabiotic states which differ in various respects from the typical 

 parabiosis just described. Thus it is possible to transplant skin and certain 

 other organs to a strange individual by means of a pedicle containing blood 

 vessels, which keeps the transplant united with the original donor ; it then 

 received blood from the latter, while at the same time it receives bodyfluids 

 from the new host, and is accessible, to a limited extent, to the action of the 

 host cells. The union between child and mother in the uterus, by means of 

 the placenta, may also be considered as a modified state of parabiosis, in 

 which both organisms lead largely an independent life and in which both 

 carry on their own metabolism, but in which to a certain degree an exchange 

 of substances may take place through the placenta. In a still wider sense, 

 the condition of symbiosis, or of parasitism, may be considered a state of 

 parabiosis, in which host and symbiont or parasite carry on essentially their 

 own metabolism and function, each in its own peculiar manner, but in 

 which substances may be exchanged between the two organisms. We are 

 concerned here with these various conditions only in so far as the action of 

 individuality differentials on strange tissues, organs, or whole individuals 

 comes into play. 



Transplantation by blood vessel anastomosis. Hoepfner (1903) first car- 

 ried out the retransplantation of an amputated leg in a dog by uniting blood 

 vessels, muscles and skin. The dog died as a result of an accident after 

 eleven days ; the vessels were found free from thrombosis ; skin and muscles 

 at the place of union between host and transplant showed satisfactory healing 

 and there was a tendency of the bones to unite. Several years later, Carrel 

 and Guthrie, Carrel, as well as Lexer and Giani, made similar experiments ; 

 but Carrel improved the method of blood vessel anastomosis and in addition 

 extended transplantation by this method to kidney, thyroid, adrenal gland 

 and ovaries. He believed that not only autotransplantation but also homoio- 

 transplantation of arteries may succeed. After a few months, the micro- 

 scopical structure of the transplanted vessels was almost, although not 

 entirely, normal. Both Carrel and Guthrie found that even after hetero- 

 transplantation of carotid from dog to cat, the vessels were normal after 

 more than one year. When rabbit vessels were grafted to a dog, the function 

 of the artery was maintained for a long time, but only the connective tissue 

 constituents of the arteries remained preserved. Not only autotransplantation, 

 but also homoiotransplantation, of kidney, thyroid, adrenal and ovary suc- 

 ceeded. The kidney functioned, although hydronephrosis and interstitial 

 nephritis were observed in some cases in the transplanted organ. Likewise, 



