280 Drs. Mott and Halliburton and Mr. Edmunds. [June 12, 



Union of the divided nerves occurs on both sides of the body, and in our 

 early experiments the nerve on the side corresponding to that on which the 

 posterior nerve roots had been divided was found to be the less excitable 

 to the faradic current. Histologically this nerve showed a looser texture, 

 and new nerve-fibres, though present, were somewhat less numerous than on 

 the control side. In these early experiments also we found that the posterior 

 cornual cells in the cervical region were atrophied, and that there was a 

 considerable overgrowth of neuroglia tissue in the posterior horn. 



Further examination (by the methylene blue and erythrosin stain) of 

 these spinal cords showed, however, that there had been a considerable 

 number of small haemorrhages in the cord, sufficient in some cases to cause 

 degeneration in various descending tracts in the cord. It, therefore, became 

 quite possible to explain the effects observed by this complication. We are 

 inclined to think that the haemorrhages are not due, or not chiefly due, to 

 mechanical injury of the cord during the operation, but are to be explained 

 by the loss of support in the cord tissue which follows degeneration of the 

 entering posterior root fibres. 



In several of the later experiments in which cord haemorrhages did not 

 occur to any great extent, we have been unable to detect any marked changes 

 in the anterior or posterior cornual cells, or any difference to stimulation 

 or in microscopic structure between the regenerated nerves of the two sides. 



This conclusion fits in with some experiments of H. K. Anderson ;* 

 "he showed that in developing animals, section of all the posterior roots 

 connected with a limb exercised no retarding influence on the development 

 of the corresponding anterior roots. 



Warringtonf has stated that when posterior nerve-roots are cut, the anterior 

 nerve cells undergo the chromatolytic change associated with inactivity. We 

 do not wish to dispute Warrington's observations which apparently were made 

 at an early date after the division of the roots. If the change does occur, it 

 can only be temporary, and in the animals which we have killed at the later 

 dates mentioned, and also some killed at earlier dates (including one killed 

 17 days after the division of the roots), it was not possible with any certainty 

 to tell by looking at the anterior nerve cells of the two sides which was 

 the side on which the posterior roots had been divided. 



In further experiments we sought to cut off the cerebral influence by 

 removing the cortical arm area of the opposite side in addition to dividing 

 posterior roots as before. In this case also the regenerated nerves of the two 



* ' Journ. of Physiology,' vol. 28, p. 499 (1902). 



t Mourn, of Physiology,' vol. 23, p. 112 (1897—98); vol. 24, p. 464 (1899); vol. 25, 

 p. 462 (1899—1900). 



