558 SURGICAL APPLIED ANATOMY. [Chap. xxiv. 



the needful sensory impulse. This impulse is re- 

 flected to the nerves controlling the bladder muscles, 

 and especially to the detrusor urinae, and by their 

 contraction the organ is emptied. The action, how- 

 ever, can be to some extent inhibited by influences 

 passing down from the brain to the lumbar centre, 

 and the tendency to a frequent discharge of urine 

 is resisted by contraction of the sphincter. When, 

 therefore, any part of the cord is damaged that lies 

 between the lumbar centre and the brain, this inhibi- 

 tion can have no effect. Immediately after the 

 accident the temporary suspension of reflex actions 

 from shock produces some retention of urine, and 

 after that the bladder empties itself at frequent 

 > intervals, the patient being unconscious of the act, 

 and unable to influence it 



If the centre itself be damaged in the lumbar cord, 

 the patient, after a little retention, will suffer from 

 absolute incontinence ; and a like result will follow if 

 the nerve connections between the cord and bladder 

 below the spinal centre have been destroyed. The 

 principal nerves connecting the medulla spinalis with 

 the bladder are the third and fourth sacral. 



The act of defsecation also is apt to be disturbed 

 in a like manner. Here there is, as in the previous 

 case, a reflex centre in the lumbar enlargement, with 

 motor and sensory nerves connecting it below with 

 the rectum and its muscles ; and also between this 

 centre and the brain are tracts, but little known, 

 along which inhibitory actions can extend. 



When the centre itself is damaged, or the con- 

 nection severed that unites it with the viscus, the 

 patient will suffer from incontinence of faeces, and 

 will be unable in any way to control the act. When 

 the cord is damaged at any spot between the centre 

 and the brain, then the act of defsecation will be 

 performed at regular intervals, without either the 



