272 Ross Granville Harrison 



of transplantation the limbs did contain fine nerve twigs. The 

 three specimens that do contain traces of nerves are those which 

 were preserved two, seven and ten days, respectively, after the 

 operation. In the first of these there is a short twig present which 

 contains several Schwann cells and fibrillae in a state of disinte- 

 gration. The same is true of the ten-day specimen. In the seven- 

 day specimen considerably more than the usual amount of tissue 

 had been transplanted and this included part of several myo- 

 tomes; hence this experiment is directly comparable to those of 

 Banchi. In the transplanted tissue several structures are to 

 be found which are undoubtedly degenerating nerves. One of 

 these is a chain of cells without any visible fibrillae; the others 

 show fibrillae in addition to the cells, though the former are indis- 

 tinct. 



The results of these experiments plainly indicate that there is 

 no progressive development of the nerve after severance of its con- 

 nection with the center. On the contrary there are rapid regres- 

 sive changes, which in the majority of cases result in the entire 

 disappearance of the nerves within a few days after they are cut 

 off from their centers. The one case, in which the larger trunks 

 were transplanted and which showed definite traces of the trans- 

 planted nerves after the expiration of ten days, may be taken as 

 indicating that larger nerves will persist longer than the finer ter- 

 minal twigs. 



Two other series of experiments have been made for the pur- 

 pose of testing in a more simple manner, the direct effect of the 

 removal of the ganglion cell upon the growing nerve fiber. It 

 was found that excision of the spinal cord in embryos of Rana 

 palustris 8.5 mm. long results in the complete disappearance of 

 the motor rami after a few days, and likewise the removal of the 

 vagus ganglion in embryos 6 mm. long brings about rapid disin- 

 tegration and early disappearance of the r. lateralis.^^ In these 

 experiments sources of contamination from anastomoses were 

 under control. The results are in entire accord with the results 

 of transplantation of limbs just described, and they show that a 



2'These experiments were made in collaboration with Mr. Laurence Selling, who will report upon 

 them later in full. 



