342 Prof. C. S. Sherrington. On Reciprocal [Mar. 9, 



to be more marked at one or another of those joints according to 

 circumstances, of which one has seemed to be the particular nerve chosen for 

 excitation. These afferent nerves have also provoked reflex relaxation of vasto- 

 crureus, adductores, quadratics femoris, semi-membranosus, gastrocnemius, and 

 soleus. These reflex results have throughout the experiments been perfectly 

 constant, in the sense that a nerve which provoked reflex contraction of 

 a certain muscle never yielded reflex inhibition of that muscle, either in 

 the same experiment or in another. The modes of stimulation of the nerves 

 were, in each case, faradisation and mechanical compression separately 

 employed for each nerve. 



Of these afferent nerves examined, some are cutaneous, some deep, 

 e.g., issue from muscles, and some contain fibres from both cutaneous and 

 deep sources. The reflex result of each was the same, in so far that each 

 provoked contraction of the flexor muscles and reflex relaxation of the 

 extensor muscles. I have shown previously* that the reflex movement 

 provoked in the limb by faradisation of skin points in all parts of the 

 surface, below the knee at least, is likewise flexion at knee, hip, and ankle. 

 Putting these results together, it seems, therefore, that whereas in some 

 reflexes, e.g., the scratch reflex and the pinna reflex, the receptive field of the 

 reflex is entirely cutaneous, in the flexion reflex of the limb the receptive 

 field is both cutaneous and deep. For reasons adduced elsewhere,^ the deep 

 receptors of the body, e.g., receptive end-organs in muscles, tendons, joints, 

 bones, etc., can be conveniently classed together as proprioceptive, the 

 immediate agent of stimulation in their case being usually not an object of 

 the environment, but a part of the body itself. On the other hand, the 

 receptors of the outer surface of the organism, e.g., the skin, receive their 

 stimulation usually more directly from the external environment, and have 

 been termed exteroceptive. $ The fields of reception of such reflexes as the 

 scratch reflex and the pinna reflex are, therefore, purely exteroceptive ; but 

 the field of reception of the flexion reflex of the hind limb is both extero- 

 ceptive and proprioceptive. The same appears to be true, so far as my 

 experiments go, of the flexion reflex of the fore limb, and also for the 

 crossed extension reflex of the hind limb and the crossed extension reflex of 

 the fore limb. The field of reception of each of these reflexes appears to be 

 both exteroceptive and proprioceptive. 



* ' Journ. of Physiology, 5 vol. 34, p. 28 ; 'Integrative Action of the Nervous System,' 

 London and New York, p. 127. 



t 'Integrative Action of the Nervous System,' pp. 130, 336, etc.; 'Ergebnisse d. 

 Physiologie,' p. 824, 1905, 



\ ' Integrative Action of the Nervous System,' loc. cit. ; i Ergebnisse d. Physiologie, 

 loc. cit. 



