ii.] ANESTHETICS 39 



your hands ; one of these the action of anaesthetics I took 

 the opportunity of examining with some care a few years ago 

 in connection with a methodical study of the action of anaes- 

 thetics on isolated nerve ; * the other retino-motor effects I 

 have not worked at myself; it rests upon the authority of 

 Engelmann, who discovered and worked the point with his 

 pupil Grijns. 



The ordinary anaesthetics carbon dioxide, ether, and chloro- 

 form influence the electrical response of the retina to light as 

 might be expected from a consideration of the physiological 

 character and conditions of the response and the relative power 

 of the anaesthetics used. With an enucleated eyeball as the 

 object of experiment, the layer to be anaesthetised is compara- 

 tively well protected by the sclerotic coat, and the effects of an 

 anaesthetic vapour are obstructed if only because its access to 

 the retina is obstructed. Still the characteristic effects of the 

 three anaesthetics are produced, although more slowly and im- 

 perfectly than in the case of an isolated nerve. Carbon dioxide 

 gives diminution followed by augmentation of the response. 

 Ether gives temporary diminution or abolition of the response, 

 followed (usually) by perfect recovery. Chloroform gives aboli- 

 tion of the response, and the abolition, once it is produced, is apt 

 to be final. 



21. Rctino-nwtor effects. The effects studied by Engel- 

 mann and Grijns are interesting in two chief particulars : they 

 indicate the possible existence of efferent fibres in that most 

 typical afferent nerve, the optic nerve (retino-motor) ; and they 

 afford some answer to a question that has no doubt occurred 

 to you, whether, namely, the electrical change occurring in an 

 illuminated retina, belongs to altered pigment or to retracted 

 cones or to both phenomena. The chief points in Engelmann's 

 observations are, that retraction of the cones and an electrical 

 effect can be produced in one eye by electrical excitation of 

 the peripheral end of its optic nerve, or of the central end of 



* WALLER." The Action of Anaesthetics on Nerve." Presidential 

 Address to the Section of Anatomy and Physiology of the British Medical 

 Association. Montreal, 1897. British Medical Journal, 1897. 



