EFFECTS OF EXPERIMENTAL LESIO 839 



also it will be noted thai after section of the posterior roots of or 



the corresponding limb hangs lower than its fellow because its muscles 



are tonel* 



Stimulation of the central end of a cul afferenl root prod 

 already been indicated, a contraction of the muscles accompanied K 

 reciprocal inhibition <>i' their antagonists, bo thai Borne definite move- 

 ment of the joint takes place. This movemenl is. however, merely a 

 flexion or extension or rotation, bu1 with no very evidenl objecl in vii 

 Tn this regard it is quite different from the purposeful movement wl 

 results from stimulation of a Bkin area, indicating, therefore, that the 

 receptor apparatus itself must contribute to the nerve impulse some- 

 thing which causes it to bring about a more perfectly integrated move- 

 ment Hi* the musculature than is the case when the nerve trunk is di- 

 rectly stimulated. 



Besides the movements of the musculature innervated from segments 

 which are beside those <>t" the stimulated afferent root, there is a gen< 

 reflex response through other centers, for example, the respiratory and 

 the vasomotor; and, in animals which are not deeply anesthetized, there 

 is also evidence of pain, stimulation of the peripheral end of the sen- 

 sory root lias of course no effecl 



THE SPINAL CORD AND BRAIN STEM 



The results of transsection of the cord have been already sufficiently de- 

 scribed. It remains to discuss the effed of total ablation or removal of 

 portions of the cord. As would be expected, there is a marked degree 

 of shod; for some weeks after ablation. During this shock the tone 

 of the sphincters and vessels is greatly depressed, so that congestion 

 and edema of the feet, diarrhea and retentio urince are marked, and 



ulcerati f the skin is practically unavoidable. After a few week-. 



however, recovery becomes evidenl u far as the blood vessels and 



sphincters are concerned, hut the skeletal musculature atrophies very 

 extensively and comes to resemble connective tissue, [f the spinal 

 ablation involves the thoracic region, for example, the affected in- 

 tercostal muscles become stiff and parchment-like; the hones ah 

 brittle, and visible perspiration can not be produced. On the other 



hand, after s time the sphincters functionate more or less normally, 



the hair is shed and renewed ill normal fashion, and the application of 

 cold to the skin causes the usual vascular reaction, it is of inter 

 that in female animals whose lumbar spinal cord has been remoi 

 pregnancy maj take place normally, followed by lactation. 



Section Just Above the Medulla. After such an operation, the aui- 



