470 THE SPINAL CORD. 



soon as a small quantity of it has accumulated in the bladder. The 

 impression which excites this discharge is accompanied by a conscious 

 sensation, but is too urgent to be resisted by the will. 



On the other hand, injury or destruction of the spinal cord in the 

 dorsal region may cut off all sensibility and voluntary power over the 

 bladder, and yet the organ may be evacuated at regular intervals by 

 the reflex action of the lumbar portion of the cord. But in diseases or 

 injuries affecting extensively the lower portion of the cord, a complete 

 paralysis of the bladder is often produced. The patient is consequently 

 unable to discharge his urine in the ordinary way, and requires to be 

 relieved by the introduction of a catheter. If this be not done, the 

 urine accumulates in the bladder; being retained for a time by the 

 elastic tissues surrounding the neck of the bladder and the urethra. 

 But after the distension of its walls has reached a certain point, the 

 mechanical resistance of the bladder becomes too great to allow any 

 further accumulation; and the urine dribbles away from the urethra as 

 fast as it is excreted by the kidneys. Paralysis of the bladder, accord- 

 ingly, first causes a permanent distension of the organ, which is after- 

 ward followed by a continuous, passive and incomplete discharge of its 

 contents. 



The spinal cord, therefore, in its character as a nervous centre, exerts 

 a general protective influence over the whole body. It presides over 

 the involuntary movements of the limbs and trunk; it supplies the 

 requisite nervous connection between different muscular actions for the 

 attitude and locomotion ; and by its control over the muscular appa- 

 ratus of the rectum and bladder, it regulates the accumulation and 

 discharge of the excrementitious products of the system. 



