On Innervation of Antagonistic Muscles. 



479 



knee on the flexor aspect of the hip. The attachment of small weights to the 

 foot has not, in my experience, increased the reflex. 



In the stepping reflex obtained when the animal is supported vertically 

 (the " mark-time " reflex) the movement is more pronounced at hip than at 

 knee and ankle. A very similar stepping reflex occurs also when the animal 

 is nearly supine. In this latter the movement is more marked at ankle and 

 knee than at hip. In this posture of the animal passive dorsi-flexion of one 

 ankle often excites dorsi-flexion of the opposite ankle, followed by extension 

 at that knee and then by plantar-flexion at that ankle. 



Fig. 1. — "Mark-time" reflex of spinal dog. The up strokes correspond -with flexions of 

 the limb, the down strokes with extensions. For the period between the two marks 

 on the signal line the reflex was interrupted by taking the limb's weight off the 

 fellow limb to that yielding the record, namely by supporting it under the knee. On 

 return of the reflex, when the limb was again allowed to hang under its own weight, 

 the reflex shows no increase beyond its previous activity. The small undulations 

 during the period of rest are due to slight swaying of the animal ; the reflex ceased 

 completely. Time is registered above in seconds. 



There is also a stepping reflex elicitable from the spinal dog when lying on 

 its side and without any marked mechanical strain either of flexion or exten- 

 sion ; this is obtained by faradisation of the skin of the opposite hind foot * 



* Sherrington, 1 Journ. of Physiol.,' vol. 33. 



