ANIMAL GRAFTS AND REGENERATIONS. 245 



mark, indeed, that in this case a grafting is made of a whole 

 complete organ, with a structure and vascular arrangements 

 which may make its development certain, while the trans- 

 plantation of a fragment of periosteum or of marrow has 

 the effect of isolating.and encysting it. 



The most exact and curious experiments that have been 

 made in animal grafting, of late years, are due to Paul 

 Bert. This learned physiologist has shown that, if the tail 

 of a young rat be cut off and inserted, after flaying it, under 

 the animal's skin, in any part of the body, it adheres to the 

 place and continues to develop there. The organ gains 

 in size almost as rapidly as in its normal conditions. Bert 

 has also practised animal layering. He flays the point of 

 a rat's tail, inserts the end in a hole made beneath the ani- 

 mal's skin, near the head, for instance, and joins the edges 

 of the two wounds by stitches at points. The parts placed 

 in contact quickly unite, and the tail, thus endowed with 

 the shape of a handle, keeps its vitality. If it is then cut 

 at any point, it is found that the fragment grafted in at the 

 head preserves its physiological properties. The vessels 

 are formed again in it, the nerves renew their life, and sen- 

 sibility returns by degrees. The rat is thus furnished with 

 a sort of trunk as much alive as its other, organs. The re- 

 turn of sensibility in this trunk proves not only the con- 

 nection of the nerve-threads of such an appendix with 

 those of the back, but also the possibility of the propaga- 

 tion of sensor nerve-action in an opposite direction to that 

 it previously followed, that is to say, the power of the 

 nerves to carry impressions in a centripetal course as well 

 as in a centrifugal one. 



Siamese grafting has been effected by Bert under ex- 

 ceedingly interesting conditions. Strips of skin are sepa- 

 rated by cutting along the opposite sides of two animals, 

 and by means of these ribbons pressed face to face, and 

 stitched together, the two subjects are sewed into union. 



