1906.] 



Regeneration of Nerves. 



271 



extensive skin incisions, anaesthesia is always found on one side of the 

 incision, varying in extent according to the direction of the incision and 

 the number of cutaneous nerves divided. It is, however, the rule for these 

 anaesthetic areas to completely recover. 



Again, when a longitudinal incision is made through the rectus abdominis 

 muscle it is very rare to find any permanent paralysis of portions of the 

 muscle, although division of its nerves must be very common. Temporary 

 paralysis, of course, must take place, but there is so little fear of ultimate 

 paralysis and atrophy of the muscle that many surgeons prefer an incision 

 through the rectus to any other method of performing laparotomy. 



To further study this point we repeated Kennedy's experiment, with the 

 variation that a portion of a nerve was not only inserted underneath the 

 skin, but a similar portion was inserted into the peritoneal cavity. This was 

 performed as follows : the peritoneal cavity of a cat was opened through an 

 incision in the left hypochondrium, and the stomach drawn up into the 

 wound. The portion of sciatic nerve which had been previously removed 

 from the same animal was laid on the anterior stomach wall. A row of 

 Lembert sutures of catgut were then passed so as to invaginate a groove of 

 tissue around the nerve ; the sutures were continued for a short distance at 

 each end of the nerve so as to completely enclose it in a sheath of stomach 

 wall lined by peritoneum. In this way there was no possibility of nerve- 

 fibres growing in from the skin, and but little possibility of their coming 

 from the stomach. 



As a control experiment a wisp of catgut was enveloped in the stomach 

 wall in a precisely similar manner. 



After 150 days, the animal was killed and the nerves examined. In one 

 case the whole of the nerve tissue had completely disappeared ; apparently 

 it had been entirely absorbed by leucocytes, and the suture line was the only 

 sign of the operation. 



But in other experiments, where the nutrition of the nerve had probably 

 been more effectually maintained, the nerve could be readily seen both in 

 the stomach wall and under the skin. It was thinner and more transparent 

 than when it was inserted. It was examined in teased specimens and in 

 sections. It can be readily teased out into its constituent fibres, and this 

 method is perhaps the most valuable one of investigating its structure. 



When thus prepared, each fibre looks like a long tube ; they have no 

 double contour and there is no trace of a medullary sheath. There are very 

 abundant nuclei which take nuclear dyes rapidly and intensely. At the 

 point where a nucleus is situated there is usually no increase in the 

 diameter of the fibre, the nucleus being either central or projecting into a 



