310 MESSRS. P. GOTCH AND V. HORSLEY 



the sciatic nerve, removing the exposed portion of each, placing it on a glass plate 

 and bringing one electrode in connection with the cross section, the other with the 

 longitudinal surface of the preparations. It will be found that in the Cat the nerve 

 difference amounts to little over '01 Daniell, whereas the cord difference amounts to '025 

 to '03 Daniell or more. That this contrast is not merely a question of cross sectional 

 area is shown by experimenting with the dorsal cord of a small (young) animal and 

 with the large nerve of a full grown adult animal of the same species, when the same 

 relations will be found to still hold good, viz., the cord difference twice to three tunes 

 the amount of that of the nerve. 



For purposes of experimental investigation however, the spinal cord was exposed in 

 the lower dorsal or lumbar region under all the precautions mentioned in the 

 paragraph upon operative procedure ; it was then divided and freed as required on 

 either the central or peripheral side of the division for 4 or 5 centims. from all its 

 attachments, the severed end was ligatured and this portion of cord raised from the 

 canal and suspended in air by a ligature, still retaining its continuity with the 

 exposed cord at its deep attachment. The raised portion was in some cases that on 

 the central side of the section, in which case the continuity with the brain was pre- 

 served, in others that on the peripheral side, in which case the connection with the 

 sciatic nerves was preserved. 



] . Amount of Difference. 



(a.) Whole Cord. If an average of the various results obtained in the case of fifty 

 Cats is taken, the exposed cord being normal and always in connection by its deep 

 attachment with a portion of cord in situ, but without distinction of the nature of this 

 attachment, it will be found that the average resting difference in the Cat is '032 

 Dauiell, the highest difference being '046 Daniell, the lowest '014 Daniell. 



A similar average of the results in nine Monkeys gives a resting difference of '022 

 Daniell, the highest difference observed being '029, the lowest '013. 



It is thus evident that the relationship between the amounts of the resting 

 difference obtainable in the Cat and Monkey holds good for both the sciatic nerve 

 and the cord, the amount in the Cat being very appreciably larger than that in the 

 Monkey. The notable increase in the size of the resting current in the cord as 

 compared with the nerve of the same species will be rendered evident if we place side 

 by side the average results of the two. Thus : 



Cat cord _ '032 _ 33 



Cat nerve " " '0095 "" 1 



Monkey cord _ -Q22 __ 4j4 

 Monkey nerve '005 1 



That this increase in the proportion of about 4 to 1 is not merely due to increased 



