€8 Sherrington 



sino-le shock. But in various other mammalian reflexes this is not the case, 

 and the " flexion-reflex " of the limb is elici table by a single induction shock, 

 either make or break, and of such slight intensity as to be imperceptible to 

 the tongue.^ 



With the single induction shock as stimulus, therefore, and with the 

 " flexion-reflex " as reaction, observations can be made on the relation 

 between intensity of stimulus and intensity of reflex response. For 

 obtaining comparable break shocks in the following observations, the 

 opening of the primary circuit has been operated by a pendulum. To 

 obviate changes in resistance, a box of 100,000 ohms has been employed in 

 the secondary circuit. The "flexion-reflex" can be readily excited by a 

 break shock, whether applied to an afferent nerve of the limb or to some 

 point of skin in the " receptive field " of the reflex. For the following 

 observations it seemed preferable to apply the stimulus directly to the 

 afferent nerve rather than to the skin. It is true that, as Baglioni^ has 

 pointed out for the frog, application to the nerve is probably not so 

 favourable as application to the skin for the obtaining of the full amount 

 of grading of the reflex. On the other hand, however, by applying the 

 external stimulus to the aflferent nerve direct, the unknown factors entering 

 into the reaction are somewhat reduced, a desideratum where so many 

 variables are perforce included. The afferent nerve to which the stimulus 

 was applied remained the same for all the experiments; it was the 

 musculo-cutaneous branch of the peroneal taken about 4 centimetres below 

 the knee. The electrodes were silver pins placed on each side of the nerve 

 5 mm. distant along its length. The direction of the current in all the 

 observations was the same. 



The " intensity " of the reflex reaction has several forms of expression.^ 

 The reflex reaction as it increases in intensity tends to involve an increasing 

 number of muscles. It also involves with greater intensity the several 

 muscles individually."* The greater reflex movement of the limb which dis- 

 tinguishes a stronger reflex effect from a weaker is probably usually due to 

 both these factors.^ In the following observations the increase of intensity 

 of reflex reaction has been examined as it occurs in the individual muscle. 

 The question of irradiation of the reflex discharge over a wider or narrower 

 field of musculature has not here been entered on. In regard to any such 

 grading of intensity of action as might be found in the individual muscle, 

 the inquiry had in view its comparison in the excitatory and inhibitory 

 sides of the reflex respectively. The " flexion-reflex " ^ is a reflex of 

 simultaneous double sign (± reflex); flexors of hip, knee, and ankle, and 



1 Sherrington, C. S., Proc. Eoy. Sue, vol. Ixxvi. B, p. 270, 1905. 



2 Baglioni, S., ibid. "^ Sherrington, C. S., Integrat. Action etc. 



■* Sherrington, C. S., Journ. of Physiol., loc. cit. ; Langendorff, 0., Nagel's Hand- 

 buch d. PhysioL, iv. i., footnote, p. 240, 1904. 



s Sherrington, C. S., Integrat. Action etc. 



" Sherrington, C. S., Proc. Roy Soc, loc. cit. ; Integrat. Action etc., p. 83 ; Ergebn. 

 d. Physiol, 1905, p. 834. 



