31G 



MESSRS. F. GOTCH AND V. HORSLEY 



minutes. This initial increase is probably of the same character as that observed 

 by DU BOIS-REYMOND, HERMANN, ENGELMANN, and others in both muscle and nerve, 

 and is in some way related to the development of changes produced by the cross 

 section. 



The difference continues very slowly to increase in the unstimulated cord, at a rate 

 of about 0001 in five minutes, this change being probably connected with interstitial 

 drying. There is, however, a marked increase in the difference when the cord is 

 aroused by successive stimulation, and this last rise is the most striking and novel 

 feature displayed by the cord : it will be treated of under the excitatory changes. 



If systemic death occurs, the difference immediately begins to decline, and this is 

 such an invariable result that we have often observed the first approach of death by 

 the behaviour of the galvanometer needle. On separation of the cord from the body 

 a similar decline occurs, the rapidity of which is shown by the following results : 



DECLINE in Difference following Systemic Death. 



From the above cases it will be seen that on systemic death the resting difference 

 declines to such an extent that in half an hour the total fall amounted to 007, 008, 

 and 009 Daniell. How far this fall is associated with the cessation of the circulation 

 in the actual portion of exposed cord under investigation is a moot point, but the 

 reasons brought forward on p, 283 with reference to the similar question in the case of 

 the sciatic nerve are applicable to that of the spinal cord. The local circulation is 

 undoubtedly seriously impaired by the exposure ; it is, therefore, rather to the 

 structural connection with the portion of cord in situ, in which the circulation is 

 adequately maintained, than to the integrity of its own blood supply that the main 

 tenance of the difference in the case of the living animal must be ascribed. It is 

 wonderful what prolonged exposure a portion of the spinal cord will sustain without 

 losing its excitability, provided only that the local conditions of adequate moisture 

 and warmth are fulfilled and tha,t a structural connection is kept up with normal 

 unexposed cord substance. 



The above decline is contemporaneous with a marked lessening of excitability. As 

 is shown in the chapter upon cord excitation, all evidence of excitatory change in 

 response to stimulation disappears a few minutes after systemic death. 



If the fragment of exposed cord is wholly removed from the animal, the difference 



