146 LEO LOEB. 



pose it might be best to select a few examples of our experiments 

 in order to illustrate some of the more important factors that 

 come into play under various conditions of transplantation. We 

 shall first discuss transplantation of pigmented skin, in the guinea 

 pig, then as examples of glandular organs, the thyroid gland and 

 kidney, and lastly the uterus as an organ containing a variety of 

 tissues, epithelium, myxoid or predeciduomatous connective tissue 

 and unstriated muscle. 



TRANSPLANTATION OF PIGMENTED SKIN IN THE GUINEA PIG. 



If we transplant black skin of the guinea pig into a defect in 

 white skin of the same individual, the black skin usually heals in 

 and even begins after a few weeks to penetrate into the neigh- 

 boring white skin. If instead we transplant it into a defect in 

 the white skin of another guinea pig, the skin may temporarily 

 heal in, but sooner or later it is cast off, in the majority of cases 

 at an early date following the grafting. In a few cases, however, 

 the transplant took. I suspect these were cases in which host and 

 donor were related to each other, so that in realitv we had to 



j 



deal with syngensio- rather than homoiotransplantation. Now 

 in these exceptional cases the black skin did not only not pene- 

 trate into the neighboring white skin, but on the contrary, it 

 gradually became paler and its pigmentation disappeared in the 

 end entirely. The black skin became transformed into white skin. 

 Microscopically we found in such cases in addition a gradual ac- 

 cumulation of lymphocytes under and in the strange epidermis. 

 The number of these cells need, however, not be very marked. 

 Lymphocytes are small cells with a relatively prominent round 

 nucleus which originate in lymph glands, gain entrance into the 

 circulation and are capable of active movement, which, how- 

 ever, is probably not as active as in the ordinary polynuclear leu- 

 cocytes. These lymphocytes, as we stated, are attracted by the 

 foreign skin, but not by the skin of the same organism. We 

 notice after this kind of homoiotransplantation, a primary in- 

 compatibility between the strange skin and its environment. As 

 a result of this incompatibility between body fluid of the host 

 and the transplant changes take place in the metabolism of the 

 latter which cause the deficient healing in of the transplant and 



