ON THE FUNCTIONAL ACTIVITY OF NERVE CELLS. 521 



living, and the alteration of response has not been due to visible disorgani- 

 sation ; moreover, where a recovery of response after more or less prolonged 

 suppression was commonly observed or not observed in cases where it was. 

 to be expected, for example, after ether, rarely after chloroform, after 

 carbonic acid, not after aconitine. I have attached importance to the 

 fact of recovery after temporary suppression as being evidence of an effect, 

 which, though no doubt physico-chemical in last resort, may nevertheless 

 be characterised as physiological. And the same remark is applicable to 

 all those cases where there is a temporary augmentation of response. 



(b) A priori it may reasonably be supposed that any alteration of 

 response depends upon some physico-chemical alteration of substance, 

 visible or invisible. The degree to which we are able to extend our know- 

 ledge of such material change de visu varies, and we may never draw the 

 distinction between organic and functional, or material and immaterial, tc 

 correspond with the distinction that may happen to exist for us between 

 visible and invisible. As regards the present investigation, it was sufficient 

 at the outset to be assured of the physiological nature of the observed 

 alterations of response ; the limit of visibility of the material alterations 

 upon which these symptoms depended became a matter of secondary 

 interest, that might or might not be of sufficient interest to excite histo- 

 logical investigation. I have been too fully occupied with the purely 

 physiological aspect of the subject to be able to give due time and care to 

 its histological prosecution, and all that I have learned in this direction, in 

 particular the fact that temjjorary alterations are visible in nerve under 

 the temporary influence of anesthetics, has been obtained from the careful 

 observations of Mr. F. S. Lloyd. From his report it appears that under 

 conditions of experiment considerably more severe than those obtaining 

 in my galvanometric investigation, alterations of structure so slight as 

 hardly to be detected without the closest examination, and in some 

 particulars difficult to distinguish from artifacts, are all that can be 

 observed. The permanent and a fortiori the temporary abolitions of 

 electrical response produced in my experiments have therefore not been 

 due to gross disorganisation. 



§ 2. The Microscopic Changes noticed in Isolated Nerve, after treatment with 

 Ether and Chloroform Vapour and with CO.^. By Mr. Llotd. 



• The nerves of the frog were invariably employed, especially the sciatic- 

 and popliteal iierves, also the dorsal cutaneous nerves. For ordinary 

 Fig. 1. "^ork a simple glass thimble was employed, in which a. 

 tightly-fitting cork was placed. The tube being half filled 

 with ether or chloroform, as desired, a frog was pithed and 

 a nerve dissected out as quickly and with as little injury 

 as possible. This was lightly stretched on the under surface 

 of the cork, and this replaced in the tube. The nerve- 

 thus having been exposed to the concentrated vapour 

 (EtjO, 50 per cent. ; CHCI3, 12 per cent.) for as long or 

 short a time as desired, the cork was withdrawn, and 

 1 per cent, osmic acid solution substituted for the chloro- 

 form or ether, the cork replaced, and the nerve ' fixed ' by 

 exposure to the osmic vapour for half to one hour. 



When, however, it was desired to study the microscopic- 

 change in the nerve simultaneously with the passage of the 

 required vapour over it, the following apparatus was 

 employed : — • 



