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VETERINARY PHYSIOLOGY 



(1) In the example given, the harmful pinch caused the 

 replacement of one reflex by another. But (2) occasionally 

 the application of a second stimulus may simply cause the 

 disappearance of the reflex in progress. 



(3) A third effect may be produced. The second stimulus, 

 if it is of a somewhat similar nature to the first, and in 

 proximity to it, may cause a simple augmentation of the 

 action. 



Fig. 36. — To show the play of dififerent ingoing neurons upon a motor neuron 

 FC to the vasto-crureus muscle e of dog in producing reflex action. 

 Stimulation of the ear, tail, forefoot, and pressure on the pad of the 

 hind foot of the same side, all cause excitation, as also do stimula- 

 tion of the shoulder of the opposite side and nocuous stimuli of the 

 opposite hind foot. On the other hand, stimulation of the slioulder 

 of the same side, as in the scratch reflex and nocuous stimuli of the 

 hind foot of the same side inhibit it. (Sherrington.) 



In both the flexor withdrawal and the extensor thrust 

 the same muscles of the thigh are used — the extensors and 

 fl.exors ; but in flexor withdrawal the extensors are inhibited, 

 while in the extensor thrust they are contracting. The 

 nerve to the extensors, therefore, in the first action carries 

 checking impulses, in the second stimulating impulses. It 

 is the common path for both kinds of outgoing impulses. 



The ingoing neurons from the body are about five times 

 as numerous as the outgoing. Each set may be looked 



