74 THE BIOLOGICAL PROBLEM OF TO-DA Y 



piece, and planted it in the connective tissue under 

 the skin of the same animal. In a few days circu- 

 lation of blood was established in the pieces of the 

 tails, by union with vessels from the connective 

 tissue in which they were embedded. Muscles and 

 nerves degenerated, but the other tissues, bones, 

 cartilages, and connective tissue, grew vigorously, 

 so that, in animals killed and examined a month 

 after the operation, the pieces of tail, implanted 

 when they were two or three centimetres long, had 

 grown five to nine centimetres long. 



The result was totally different when the trans- 

 plantation was made from one species to another. 

 When the tip of the tail of a Mus decumanus or 

 a Mus rattus was transplanted to a squirrel, guinea- 

 pig, rabbit, cat, dog (or vice versa), either extensive 

 suppuration took place, and the piece was extruded, 

 while sometimes the subject of the experiment 

 died ; or, after a less turbulent course, the alien 

 piece was absorbed. The continuance of life and 

 growth in the piece only took place when the 

 two animals concerned were allied very closety. 

 Thus success followed transplantation from Mus 

 rattus to Mus decumanus (or vice versa), but not 

 when it was from Mus sylvaticus to Mus rattus. 



The recent experiments of A. Schmitt and Bere- 

 sowsky lead to the same conclusion. The former 

 succeeded in making pieces of living bone ' take ' 

 only when the transplantation was from one indi- 

 vidual to another of the same species, or to another 

 part of the same individual. Beresowsky trans- 

 planted pieces of frog's skin to the dog and the 



