ANIMAL GRAFTS AND REGENERATIONS. 243 



tree to which it is united, it remains always physiologically 

 distinct from it. The case is not the same with animals. 



Animal grafting consists, in a general way, in fixing 

 upon some point in an individual a part taken from another 

 point in the same individual, or from a different subject, and 

 in effecting the connection of the grafted part with the or- 

 ganism which serves for its siipport, in such a way that it 

 may become completely incorporated with the latter, and 

 may live with the same life, and follow the same physio- 

 logical course. We may thus transfer from one animal to 

 another either fragments of tissue, or whole organs in their 

 completeness, or simple anatomical elements. The cells of 

 the choroid of the eye, placed beneath the skin of an animal, 

 preserve their vitality in that new region, and there even 

 become the starting-point for a more or less extensive forma- 

 tion of similar cells. Transfusion of blood is nothing but 

 the introduction of red globules borrowed from one organ- 

 ism into a different organism. This operation succeeds, 

 even when the blood passes from one individual to another 

 of quite a different species. Thus the blood of a mammal 

 may be introduced into the veins of a frog, and those glob- 

 ules be found in the latter after some time, still living*, and 

 easily distinguishable as those of the superior being. We 

 can without difficulty graft upon a cock's comb either spurs 

 taken from the same bird, or teeth from a mammal ; but 

 such facts have hitherto had no interest other than that of 

 curiosity, and need not detain us. 



We have seen that bones may readily be reproduced by 

 means of the periosteum. This property has suggested to 

 some experimenters the idea of transplanting fragments of 

 periosteum into different parts, so as to learn whether they 

 would there occasion a formation of bone. Oilier, among 

 others, has shown that the periosteal membrane, quite sepa- 

 rated from the bone and grafted at some remote point, pro- 

 duces upon its deeper side a new bone. He effected a like 



