202 Prof. C. S. Sherrington and Miss S. C. M. Sowton. [June 29, 



sartorius preparation of the branch to that muscle from the femoralis nerve of one limb. 

 (2) Muscles resected : glutei tensor fasciae femoris, psoas and psoas parvus, and all 

 muscles attached to the femoral trochanters and intertrochanteric line. (3) The animal 

 lying supine, with hips and knee semi-flexed, steel drills are inserted into the innominate 

 bone, the outer femoral condyle and the lower end of tibia in both limbs ; these drills are 

 then clamped to heavy immovable uprights on the experiment table. These steps, as 

 well as the whole of the preceding decerebration, are carried out under deep chloroform 

 narcosis. For registration of the results a thread from the freed muscle tendon is carried 

 over a light running pulley to a horizontal myograph. The tension of a light spiral 

 spring is arranged to stretch the muscle to about its ordinary resting length. For 

 stimulation of the afferent nerve or nerves we have employed faradism, or series of brief 

 constant currents of alternating direction given by a v. Kries rotating rheonome* fed by 

 four Leclanche cells, a graduated 100 ohms resistance box being in the main circuit. 

 The electrodes have been non-polarisable, either of the du Bois-Eeymond clay pattern or 

 of the Utrecht pattern devised by Noyons. 



The general plan adopted for the examination of the reflex effect of any 

 particular afferent upon the flexor centre consisted in throwing that centre 

 into reflex excitement as documented by contraction of the flexor muscle 

 attached to the myograph, and then, while that contraction was in progress, 

 stimulating the afferent nerve whose special influence on the centre it was 

 desired to observe. This latter stimulation may be termed the intercurrent 

 stimulation ; the stimulation which provides the background contraction, 

 against which the effect of the intercurrent stimulation has to show, may he 

 termed the background stimulation. 



3. Kbsults. 



i. Influence on the Knee Flexor (semitendinoms) exerted by Afferent 

 Nerves of the Contralateral Hind-limb. 



The afferent nerves tested have been contralateral peroneal and popliteal, 

 either separately or both together. The background excitation has been 

 provided by stimulation of the corresponding nerves of the ipsilateral limb. 



The effect of the contralateral afferent as thus tested is preponderantly 

 inhibition. This preponderance of inhibition is very great. It holds for a 

 wide range of intensities of stimulation. Its degree may be sufficient to 

 entirely efface all trace of the background contraction. The inhibition is 

 stronger the stronger the intercurrent stimulus (fig. 1, a, b, c), but it results 

 in many cases from even quite weak intensities of stimulus. 



With weak intensities of contralateral stimulus the effect is, however, not 

 always inhibition. Such stimulation quite frequently causes contraction, 

 i.e. augments the intensity of the contraction (fig. 2, a, c ; fig. 3, b). The 

 amount of contraction which it provokes is never in our experience large, 

 * E. Metzner, f Archiv f. Physiologie,' 1893, Supplement-Band, p. 84. 



