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 support, 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 blocd 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. Ollier, 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 
