1906.] 



Regeneration of Nerves. 



269 



animals (monkeys and cats) have been carried out at King's College, London, 

 by two of us (W. D. H. and A. E.), using anaesthetics (ether and chloroform) 

 during all cutting or stimulating operations and with strict antiseptic 

 precautions. The histological portion of the research has been carried out 

 by the third (F. W. M.). 



(1) Experiments in which Union of Central and Peripheral Ends was 



Prevented. 



In some of our previous work we noticed that the excision of any inch 

 or so of nerve was entirely inefficient to prevent union of the two ends 

 together ; we were later aware, from a preliminary communication made by 

 Langley and Anderson* of their results, that the peripheral end is often 

 invaded by new nerve-fibres from the nerves in skin and muscle divided in 

 the operation. 



We, therefore, made extremely small incisions, and the parts were 

 separated from the nerve trunks by the handle of the scalpel, and with 

 as little cutting as possible. In cats one incision over the buttock allowed 

 us to divide the sciatic nerve high up ; another in the ham enabled us to 

 divide the two popliteal nerves. The intervening portion of the sciatic 

 nerve, about 4 or 5 inches long, could then be easily pulled out. Additional 

 security to prevent union with central fibres was in some cases obtained by 

 enclosing the upper end of each' popliteal nerve in closed caps made out 

 of small sterilised drainage tubes about half an inch long. A period of 

 100 to 150 days was then allowed to elapse in order that if regeneration was 

 going to occur in the peripheral segments of the nerve it might have an 

 opportunity of doing so. At the end of this time the animal was again 

 anaesthetised and the nerves tested by electrical stimulation. In all cases 

 they were entirely inexcitable to strong faradic currents, and the wasted 

 muscles supplied by these nerves had also largely lost their power of response 

 to this form of stimulation. To the naked eye the nerves were pale. The 

 animals were then killed and the nerves subjected to microscopical 

 investigation, but they were found to show no trace of regeneration. The 

 chains of neurilemmal cells, without a sign of either axis cylinder or 

 medullary sheath, were all that could be seen, and in those cases of later 

 date where the nerves had been placed in tubes it was very difficult to 

 recognise any nervous structure whatever. 



* 'Proc. Physiol. Soc.,' December 13, 1902 ; ' Journ. of Physiol.,' vol. 29, p. ii. 



