I5O LEO LOEB. 



later date. After autotransplantation kidney tissue usually re- 

 mains preserved. 



We have begun comparative studies of auto and homoiotrans- 

 plantation in other species. There are indications that in prin- 

 ciple conditions are similar in those species which we have begun 

 to study, but there may exist some quantitative and perhaps also 

 some qualitative differences in different species, just as we found 

 certain differences in the behavior of the thyroid and kidney. 

 Thus to mention only one difference, we found that in the rabbit 

 the polynuclear leucocytes are much more prominent after trans- 

 plantation than in either rat or guinea pig. 



SYNGENESIOTRANSPLANTATION. 



If instead of transplanting the thyroid gland in the guinea pig 

 into not related individuals of the same species, we transplant it 

 into nearly related individuals of the same family, for instance 

 from brother to brother or sister, or from parents to children, we 

 find an intermediate condition between the results of auto and 

 homoiotransplantation, or rather we find all degrees of an inter- 

 mediate condition. Thus while after autotransplantation lympho- 

 cytes are almost absent and after homoiotransplantation they 

 usually begin to become prominent during the latter part of the 

 second week, they may after syngenesiotransplantation, appear 

 as late as the second half of the fourth week ; sometimes- they 

 may appear somewhat earlier or at other times later. But they 

 usually end by destroying the transplant even in relatives. We 

 find therefore a noticeable delay in the reaction on the part of the 

 host. Evidently at first the metabolism of the syngenesiotrans- 

 plant is little altered by the body fluids of the host. Gradually, 

 however, the alteration becomes here also sufficiently strong to 

 attract the lymphocytes. As we have stated above the vascular 

 and connective tissue reaction on the part of the host tissue usu- 

 ally takes place between the seventh and twelfth days after trans- 

 plantation, at a time, therefore, when the alteration of the metab- 

 olism has usually not yet become very marked. The blood and 

 lymph vessel supply may therefore in the case of svngenesio- 

 transplantation be as satisfactory as after autotransplantation, al- 

 though later the lymphocytes begin their destructive work. There 



