GRAFTING AND REGENERATION 1/9 



at all with the body of a dog or of a cat. Bert bent over the tip of 

 the tail of a rat, and grafted the distal end into the skin of the back 

 of the same animal. After the tip had established union with the 

 surrounding tissues, the tail was cut off at its base. The grafted tail 

 remained alive, but did not regenerate at its free end. 



There are several cases described by pathologists in which the skin 

 of one mammal has been transplanted to another. The transplanta- 

 tion of the skin of the negro upon a white man has been brought 

 about, but the evidence as to what subsequently happened is contradic- 

 tory. It appears that while in many instances the transplanted skin 

 has remained alive for a time, yet later it was thrown off by new skin 

 growing under it and replacing it. 



Leo Loeb has described a curious instance of grafting pieces of 

 skin of different colors in the guinea pig. If a piece of black skin 

 from the ear of a guinea pig is grafted upon the white ear of another 

 animal, it unites and continues to live, but if a piece of white skin is 

 grafted upon a black ear, it is slowly thrown off and replaced by 

 new black skin that has regenerated around the edge of the graft from 

 the tissue of the black ear. 



In the literature of pathology there are many cases described in 

 which parts of the body of mammals, particularly internal organs, 

 have been grafted in unusual regions. The results have not 

 always been the same, for while in some cases it appears that the 

 operation has succeeded, in others the grafted part is subsequently 

 absorbed, and in still other cases the graft may be at first partly 

 absorbed and later begin to grow again. It appears that the estab- 

 lishment of an adequate blood supply is the most important element 

 of success. Ribbert, who has made an extensive and successful series 

 of experiments, has stated that the grafting takes place better when 

 small pieces of an organ are used, since these can draw immediately on 

 the surrounding regions for their oxygen, etc., while larger pieces are 

 found to break down in the interior, owing to the fact that this part is 

 too far removed from the supply of oxygen, food, etc. After the grafted 

 piece has established a blood supply of its own, it may continue to 

 grow. Ribbert transplanted small pieces of different tissues of the 

 rabbit and guinea pig in, and upon the surface of, the lymph glands 

 of the same or of another individual. The lymph gland was chosen 

 because small pieces of tissue can be afterwards easily detected. A 

 small piece of tissue about as large as a pin's head is cut off from 

 whatever tissue is to be grafted, and as quickly as possible placed in 

 a small cleft made in the lymph gland. After several days, weeks, or 

 months, the gland is removed and the graft examined by means of 

 serial sections. 



Most of the experiments were made with " epithelial organs," and 



