282 Miss S. C. M. Sowton and Mr. J. S. Macdonald. [Dec. 10, 



(2.) There is no essential difference between the nerves of frogs, 

 mammals, and birds as regards their negative variation, excitability, 

 and reaction to anaesthetics. 



(3.) There is a marked difference in the extinction point for heat. 

 The negative variation in frog's nerve is abolished at 40 — 42° C, in 

 rabbit's nerve at 48 — 49°, in pigeon's nerve at 53°. 



(4.) This extinction point corresponds closely with the first coagula- 

 tion point of the body proteids, where these are known, and thus 

 coagulation is probably the cause of the permanent loss of irritability 

 of the nerve. 



(5.) The point at which the nerves are paralysed by cold is - 3° "5 

 in the frog, - 1 0, 4 in the hedgehog, +3°-8 in the rabbit, and + 6°*9 in 

 the pigeon. 



It gives me great pleasure to acknowledge my indebtedness to 

 Dr. A. D. Waller for his great kindness and assistance in everything 

 connected with this paper. 



*' On the Decline of the Injury Current in Mammalian Nerve, and 

 its Modification by Changes of Temperature. Preliminary 

 Note." By S. C. M. Sowton and J. S. Macdonald. (From 

 the Thompson-Yates Laboratory of Physiology, University 

 College, Liverpool.) Communicated by Professor C. S. 

 Sherrington, F.B.S. Eeceived December 10, 1902, — Bead 

 February 12, 1903. 



The sciatic nerve of a freshly-killed frog led off from transverse 

 section and longitudinal surface to a galvanometer, gives a current of 

 injury which, as Engelmann* and others have pointed out, is greatest 

 immediately after the section has been made. If tested at frequent 

 intervals, it is found that from the outset the E.M.F. rapidly 

 diminishes. A continuous record of the decline of the current may 

 be obtained, by photographing the movement of the galvanometer 

 spot, using for the purpose the method devised by Dr. Waller, and 

 fully described in his papers.! The nerve with its electrodes being 

 inclosed in a moist chamber, such an observation may be prolonged 

 almost indefinitely. The curve is convex to its abscissa, the decline 

 being rapid at first and gradually diminishing in speed. 



If the injury current of fresh mammalian nerve be examined in 

 a similar way, the records show in many cases a marked difference 

 of curve, the decline being often very gradual; some records even 



* Engelmann, ' Pfluger's Archiv,' toI. 15, pp. 116 — 148. 



f S. C. M. Sowton, ' International Congress,' Cambridge, 1898. 



