246 NATURE AND LIFE. 



After a few days the connection has grown cqmplete, and 

 we have such a pair as the Siamese twins. Bert kept two 

 white rats thus banded together for more than two months ; 

 but they lived on such bad terms that at the end of that 

 time it was necessary to separate them. By poisoning one 

 of two animals of such a brace, the other is poisoned also, 

 thus proving that there is complete mutual circulation of 

 blood. Bert effected like graftings between the white rat 

 and the Norway rat, and between the white rat and the Bar- 

 bary rat. He attempted to perform them between animals 

 of different species between a rat and a Guinea-pig, be- 

 tween a rat and a cat but the success was never complete ; 

 only the beginning of adherence was obtained. Still this 

 failure seems to depend less on the incompatibility of the 

 tissues themselves than on the difficulty of keeping animals 

 so little disposed to live harmoniously together in the ne- 

 cessary state of quiet. Once more, Balbian succeeded in 

 uniting two fragments of tails taken from two different 

 young bull-heads, so as to obtain a physiological adhesion 

 for a certain length of time. 



If the interest attached to such experiments is rather 

 philosophic than practical, a point to be considered here- 

 after, this is not the case with those which obtain as results 

 what are called epidermic grafts. These indeed have had 

 the privilege of attracting the highest degree of attention 

 from physiologists, and particularly from surgeons. We 

 owe to a Swiss surgeon, Reverdin, formerly an interne of 

 the Paris hospitals, the discovery and the first application 

 of these. Whenever, after a surgical operation, a burn or 

 a wound, the skin over a certain extent of surface is de- 

 stroyed, the void produced is filled up only very slowly 

 by means of a growth of scar-tissue. In spite of the 

 use of the most judicious methods of dressing, the ex- 

 posed surface is never restored but with difficulty. In 

 seeking a remedy for this grave inconvenience, Reverdin 



