THE SPINAL CORD AS A REFLEX CENTRE ' 337 



The results may be briefly summarised as follows : 



1. The period of shock lasts from one to three weeks ; during this time, in addi- 

 tion to the complete abolition of voluntary movement and sensation in the parts 

 below the lesion, the muscles are flaccid and toneless, and all reflexes are absent, 

 except those affecting the sphincters of the bladder and rectum. These are found 

 strongly contracted as early as the third day after the injury. There is in consequence 

 retention of urine and faeces ; the former, if not relieved, gives rise to distension of 

 the bladder and a dribbling incontinence due to overflow. 



2. As the shock passes away, certain reflex functions of the cord return. The first 

 reflex which appears is the ordinary flexor reflex ensuing on painful stimulation of the sole 

 of the foot. At its earliest appearance the first effect is adduction and flexion of the 

 toes ; but, with increased recovery of excitability, such a stimulus gives rise to a 

 flexor reflex consisting of flexion at the hip, adduction of the thigh, flexion of the knee 

 and the ankle, and extension of the toes. 



In some cases this flexor reflex affects also the opposite Limb, but there is little or 

 no trace of the crossed extensor reflex observed in the spinal dog. Later on there 

 is some return of reflexes also in the extensor muscles, specially marked as regards the 

 deep reflexes, so that the knee-jerk may be obtained. 



The visceral reflexes return shortly after the flexor reflex has made its appearance. 

 Thus, if the bladder has been kept from over-distension, it begins to void itself naturally 

 at a certain degree of distension, varying from 300 to 500 c.c. In this act of micturition, 

 the contraction of the detrusor is associated with relaxation of the sphincter, so that the 

 emptying of the bladder is complete. In the same way the rectum may empty 

 itself when its distension attains a certain degree, and def secation can always be elicited 

 by the injection of 8 ozs. of fluid into the rectum. 



Stimulation of the neighbourhood of the genitals, but especially of the glans penis, 

 causes erection, which may be followed by emission of semen. This reflex of coitus is 

 generally associated with strong movement of flexion of the lower limbs and contraction 

 of the rectus muscles of the abdomen. 



The main points in which the spinal man differs from the spinal dog are in the dimin- 

 ished localisation of response and in the almost complete suppression of the extensor 

 reflexes. On account of the absence of local sign, almost any stimulus, if sufficiently 

 intense, tends to evoke what has been termed a ' mass reflex,' in which there is flexion 

 of both legs, and contraction of the abdominal muscles as well as of the bladder and 

 rectum, and frequently profuse sweating over all parts of the body below the injury. 



The diminution of the extensor reflex as compared with the spinal dog points to the 

 gradual shifting of the postural reflexes towards the upper part of the central nervous 

 system which accompanies the rise in the complexity of this system. 



It should be noted that these reflex activities of the cord in man are only seen in 

 their full development provided that means are taken to ward off septic disorder, either 

 from bed-sores or infection of the urinary passages. Without extreme care general 

 infection is apt to occur by one or other of these channels, and then the separated spinal 

 cord very rapidly loses the whole of its reflex powers. 



