462 THE SPINAL COED. 



street, or even a current of air upon the skin, may be sufficient to throw 

 the muscular system into severe spasmodic action. The reflex irrita- 

 bility of the spinal cord may, therefore, be increased or diminished by 

 various causes acting upon it from without. 



Reflex Action of the Cord in Warm-blooded Animals and in Man. 

 In the frog, as well as in other cold-blooded animals, the reflex action 

 of the spinal cord lasts for a comparatively long time after decapitation 

 or the stoppage of the circulation ; continuing sometimes, if the animal 

 be kept in repose and sufficiently cool and moist, for twenty-four hours 

 or even longer. In the warm-blooded animals, it disappears much more 

 rapidly ; and it must be sought for, if at all, within a very short time 

 after death, since a nearly constant supply of blood is essential in these 

 animals to a continuance of the physiological action in every part of the 

 nervous system. If artificial respiration be kept up, however, so as to 

 maintain the circulation, the reflex action of the cord will continue to 

 manifest itself, independently of the brain ; and the same thing may be 

 accomplished, by dividing the spinal cord in the lower cervical or upper 

 dorsal region below the origin of the phrenic nerve. The animal then 

 continues to breathe by means of the diaphragm ; and although deprived 

 of both sensibility and voluntary motion in the posterior limbs, move- 

 ments of the leg are produced by pinching the skin of the foot. 



Robin has observed the phenomena of reflex action of the cord, after 

 decapitation, in man, in the case of an executed criminal whose body 

 was subjected to examination. The reflex muscular contractions were 

 produced about one hour after the execution. 1 " While the right arm 

 was lying extended in an oblique position by the side of the trunk, 

 with the hand about 25 centimetres distant from the upper part of the 

 thigh, I scratched with the point of a scalpel the skin of the chest at 

 the areola of the nipple, for a space of 10 or 11 centimetres in extent, 

 without making any pressure upon the subjacent muscles. We im- 

 mediately saw a rapid and successive contraction of the great pectoral 

 muscle, the biceps, probably the brachialis anticus, and lastly the mus- 

 cles covering the internal condyle." 



" The result was a movement by which the whole arm was made to 

 approach the trunk, with rotation of the arm inward and half-flexion of 

 the forearm upon the arm ; a true defensive movement, which brought 

 the hand toward the chest as far as the pit of the stomach. Neither 

 the thumb, which was half bent toward the palm of the hand, nor the 

 fingers, which were half bent over the thumb, presented any move- 

 ments." 



" The arm being replaced in its former position, we saw it again exe- 

 cute a similar movement on scratching the skin, in the same manner as 

 before, a little below the clavicle. This experiment succeeded four 

 times, but each time the movement was less extensive than before ; and 



1 Journal de 1'Anatomie et de la Physiologic. Paris, 1869, p. 90. 



