548 MICTUKITIOK [BOOK n. 



existence of a similar micturition centre in man, placed higher 

 up in the cord than the corresponding ' genital ' centre govern- 

 ing the genital organs. 



Moreover we have, in the case both of man and of other 

 animals, experimental and other evidence that contraction of 

 the bladder is frequently brought about by reflex action. Thus 

 the pressure within the bladder when observed for any length 

 of time is found to be subject to considerable and manifold 

 variations. Over and above passive changes in pressure due 

 to the respiratory movements, through which the bladder is 

 pressed upon at each descent of the diaphragm, active contrac- 

 tions, of a strength inadequate to bring about micturition, are 

 from time to time observed. These in some instances appear 

 to be spontaneous, or to be the result of emotions, but they 

 may be readily induced in a reflex manner, by stimulating 

 various sentient surfaces or sensory nerves. And common ex- 

 perience affords many instances where vesical contractions thus 

 brought about in a reflex manner acquire strength adequate to 

 empty the bladder. 



Observations of vesical pressure may be most conveniently carried 

 out by introducing into the bladder a catheter connected with a water 

 manometer and a registering apparatus, and so arranged as to allow 

 fluid to be driven into or received from the bladder at pleasure. 



348. Involuntary micturition obviously of reflex nature 

 has frequently been observed in cases of paralysis from disease 

 of or injury to the spinal cord ; and the involuntary micturition 

 which is common in children, as the result of irritation of the 

 penis and genital organs, and which sometimes occurs in the 

 adult as the result of emotions, or at least sensory impressions, 

 appears to be the result of reflex action. In these several cases 

 we may fairly suppose that the centre in the spinal cord is 

 affected by afferent impulses reaching it along various sensory 

 nerves or descending from the brain. Hence we are led to the 

 conception that when we make water by a conscious effort of 

 the will, what occurs is not a direct action of the will on the 

 muscular walls of the bladder, but that impulses started by 

 the will descend from the brain after the fashion of afferent 

 impulses and thus in a reflex manner throw into action the 

 micturition centre in the spinal cord. Nor is this view nega- 

 tived by the fact that paralysis of the bladder, or rather ina- 

 bility to make water either voluntarily or in a reflex manner, 

 is a common symptom of cerebral or spinal disease or injury. 

 Putting aside the cases in which the reflex act is not called 

 forth because the appropriate stimulus has not been applied, 

 the failure in micturition under these circumstances may be 

 explained by supposing that the shock of the spinal injury or 



