FUNCTIONS OF THE KIDNEY 89 



offers a temporary obstacle which is overcome by gentle 

 pressure. The elongated urethra of old prostatic cases 

 need only be mentioned. 



Nerve Control. The subject of nerve control is not 

 completely understood. That there is a center control- 

 ling micturition in the lumbar cord and that sensory 

 nerves pass from the bladder to the cord and motor 

 nerves from the cord to the bladder, is clear, but the ex- 

 act paths are not so well known. That this center, like 

 that for defecation, is under the control of the will in 

 adult life is a matter of daily observation ; but that this 

 control is acquired is plain from the habits of infancy 

 and from the involuntary passages of urine and feces in 

 the unconsciousness of severe illness, is equally obvious. 



