8 Mr. G. J. Komanes on the [May 4^ 



materially to elucidate the subject of the mode of flow of water round 

 bends in pipes, and the manner in which bends cause augmentation of 

 frictional resistance in pipes, a subject in regard to which I believe 

 no good exposition has hitherto been published in any printed books or 

 papers ; but about which various views, mostly crude and misleading, 

 have been published from time to time, and are now often repeated, but 

 which, almost entirely, ought to be at once rejected. 



VI. ^''On the Modification of the Excitability of Motor Nerves 

 produced by Injury^'^. By Gr. J. Romanes,, M,A., F.L.S. 

 Communicated by Prof. Sanderson^ M.D., F.E.S. Received 

 April 13, 1876. 



§ 1. If the gastrocnemius of a frog be placed in a horizontal direction 

 on non-polarizable electrodes with its convex surface uppermost, one 

 may generally observe that the muscle is somewhat more sensitive to 

 minimal stimulation, supplied by closure of the constant current, when 

 the femoral end rests on the kathode, than when this end rests on the 

 anode. Conversely, under similar circumstances the gastrocnemius is 

 more sensitive to minimal stimulation, supplied by opening of the con- 

 stant current, when the femoral end rests on the anode, than when this 

 end rests on the kathode. In view of the other facts of electrotonus, the 

 present ones are of interest ; because, as the sciatic nerve enters the gas- 

 trocnemius near the femoral end of the latter, and then spreads out its 

 peripheral ramifications as it advances, in the experiments just mentioned 

 one electrode is in almost immediate contact with the nerve-trunk where 

 it enters the muscle, while the other electrode supports the part of the 

 muscle that contains only peripheral nervous elements. It is therefore 

 to be expected, upon the theory of electrotonus, that the muscle under 

 these conditions should prove itself most sensitive to the closing shock 

 when the nerve-trunk rests on the kathode, and most sensitive to the 

 opening shock when the nerve-trunk rests on the anode. 



It is to be observed, however, that although this expectation is in most 

 cases fulfilled, it is not so invariably. Diferent gastrocnemius muscles, 

 though treated as far as possible in exactly the same way, manifest con- 

 siderable differences, both in their general sensitiveness to electrical sti- 

 mulation, and in their relative sensitiveness to interruptions of the ascend- 

 ing and of the descending currents. Even the same muscle, if rapidly 

 prepared, will generally be found to undergo fluctuations in these respects 

 from minute to minute. Attributing this fact to the unnatural conditions 

 which the experiment imposed on the process of nutrition, I conducted 

 some observations on muscles while they were still attached to the body 



* For further details, remarks, statements of methods, &c., see a fuller notice in the 

 forthcoming (July) Number of the 'Journal of Anatomy and Physiology.' 



