478 



On Innervation of Antagonistic Muscles. Ninth Note. — Successive 



Spinal Induction. 



By C. S. Sherrington, F.E.S. 



(Received January 31, — Eead February 15, 1906.) 



(Physiology Laboratory, University of Liverpool.) 



It was previously* pointed out that in various reflex reactions inhibition is 

 succeeded by marked exaltation of activity in the arcs inhibited. This after- 

 effect may be figured as a sort of rebound from inhibition. 



An example is the following. When a dog in which the spinal cord has 

 been transected in the thoracic region is, the period of shock having passed, 

 supported so that its spine is vertical and its hind limbs hang freely, these 

 latter begin to perform a rhythmic stepping movement. This is the reflex, 

 termed by Goltz the mark-time reflex. The tempo of this stepping differs, in 

 my experience, in different dogs and at different times in the same dog. It 

 may be as frequent at 22 steps of each leg per 10 seconds or .as slow as seven 

 steps in that period. It will persist in some animals for 20 minutes at a time. 

 After! some minutes' duration its amplitude usually becomes less and the 

 movement on the whole less regular. For the first minutes of duration it is 

 however regular and shows little variation. 



The stimulus which excites this reflex has not been traced with exactitude. 

 It persists after severance of the sciatic trunk not including the hamstring 

 nerve. Freusbergf inclined to attribute it to afferents belonging to the 

 "muscular sense," and especially to those connected with parts put under 

 strain in the passive attitude given to the limb under its own weight. It is 

 closely similar to the stepping reflex studied by PhilippsonJ in the dog sup- 

 ported with spine horizontal. That it is initiated by the stretch of some tissue 

 above the knee and especially on the flexor aspect of the hip may be argued 

 from its immediate cessation when the dependent limb is supported from 

 drooping by lifting the lower end of the thigh slightly from underneath by a 

 prop placed just above the knee. Such support, in my experience, usually 

 causes cessation of the reflex in the unsupported (fig. 1) as well as in the 

 supported limb and it does not matter which of the two limbs is supported. 

 The main stimulus, therefore, seems bilateral in origin, and to lie above the 



* ' Eoy. Soc. Proc.,' B, vol. 76, p. 160. 



t ' Pfliiger's Archiv,' vol. 8. 



% Heger's ' Travaux de Laboratoire,' Bruxelles. 



