234 



Prof. C. S. Sherrington. Nervous Rhythm [Feb. 3, 



cutaneous, obturator, internal saphenous and branch to the sartorius and pectineus. The 

 peroneal of each limb was ligated tightly at its entrance into tibialis anticus just below 

 knee. This procedure leaves the vastocrureus muscle of each limb the muscle operative 

 in or on the limb. A steel drill in the condylar end of each femur is clamped to a heavy 

 upright in such a position that, the preparation being supine, the two femora are nearly 

 vertical and are parallel, and both hips are flexed to about a right angle. The root of 

 the tail is fixed to the table by a steel pin. The leg is removed one-third down the tibia, 

 and into the free end of that bone a fine steel pin is set ; to this the thread attached to 

 the myograph lever is fastened. The angle made by the tibia with the thigh varies with 

 the degree of contraction of vastocrureus, and, the preparation being decerebrate, that 

 muscle exhibits tonus, i.e. maintains the standing posture. 



The resistance to the contraction of each vastocrureus was provided by the weight of the 

 remaining portion of the limb below the knee and the adjustable tension of a light coiled 

 wire spring attached to the lever of the myograph near its axis. The resistance was made 

 as nearly similar as possible for both the right and the left muscle. The peroneal nerve 

 on each side was stimulated with platinum electrodes, 4 mm. apart and placed with the 

 nerve-trunk obliquely between them. The pair of electrodes was inserted sidewise 

 through a glass tubulure in the wall of a glass tube, in M'hich lay the ligated nerve itself. 

 The muscles and skin around and over the electrode and tube were brought together and 

 stitched. For flexor observations the psoas and tensor fascias femoris were employed and 

 isolated, the animal being prone. 



For stimulation a pair of similar Leeds induction coils were used, one for the right 

 nerve, the other for the left. In the secondary circuit of each a resistance box of 

 100,000 ohms was introduced. A double switch connected to the circuits for both nerves 

 allowed the coils to be interchanged for the two nerves at will, furnishing some oppor- 

 tunity of testing the approximate equality of the two circuits and of the relative 

 excitability of the two nerves. 



The right and left vastocrurei, thus completely isolated in each limb, 

 but retaining blood and nerve supply and natural attachments quite intact, 

 form a symmetrical pair of extensor muscles. Under the reflex action of, 

 for instance, an afferent nerve of either limb, reciprocal, innervation obtains 

 for them as it does for an antagonistic muscle-pair. As shown, the afferent 

 of each limb relaxes the ipsilateral vastocrureus by reflex inhibition, and 

 causes the contralateral to contract by reflex excitation. The motor centre 

 of the contralateral extensor reacts therefore to the afferent in the same 

 direction as does that of the flexor of an ipsilateral antagonistic pair. 



For the observations on double reciprocal innervation required I employed 

 symmetrical afferent nerves, usually the peroneals, sometimes the popliteals. 

 With simultaneous stimulation of both right and left nerves algebraic 

 summation of the excitatory and inhibitory effects is of course the result.* 

 Over a certain range of combinations this summation is readily observable 

 because it results in contractions not wholly suppressed but of various 

 grades of submaximal intensity. Somewhere within this restricted range 

 of combinations of the opposed stimuli should lie the neutral point sought 



* Vide supra, p. 226. 



