VOLUNTARY CONTROL OF MICTURITION. 345 



flow, the free escape from the bladder through the wide tube having 

 prevented any rise of intravesical tension. Von Zeissl performed his 

 work in von Basch's laboratory, and looks upon hie experiments as 

 confirmatory of the theory of crossed innervation already put forward 

 by von Basch. He regards the hypogastric nerve as motor for the 

 circular, and inhibitory for the longitudinal (detrusor) fibres of the 

 bladder, the nervi erigentes having the reverse effect. Courtade and 

 Guyon l also conclude that the pelvic nerve is motor for the longitudinal, 

 the hypogastric for the circular fibres. I have already mentioned, 

 however, that there is, according to Griffiths, no demarcation to be 

 made out between circular and longitudinal or oblique fibres, all being 

 apparently continuous with one another. 



The nerve centre which presides over the tonus and contraction of 

 the bladder is situated in the lumbar spinal cord. If this centre and 

 its connections be intact, micturition may be carried out normally, 

 even after section of the cord in the dorsal region. The centre can 

 be excited reflexly by stimulation of almost any sensory nerve, such as 

 the sciatic or the fifth nerve. 2 In many cases where, in consequence of 

 obstruction to the passage of impulses from the higher parts of the 

 central nervous system, micturition is delayed, this act may be 

 excited by the application of cold or hot sponges to the perineum, 

 and it is well known that almost any irritation of the pelvic organs 

 in children may give rise to reflex involuntary micturition. 



The mechanism of micturition. — It is evident that the reflex act 

 of micturition is originated by afferent impulses ascending to the centre 

 in the lumbo-sacral cord, and started either by the increasing tension of 

 the bladder wall (most probably), or by stimulation of the urethra. 

 According to Goltz, 3 Kuss, 4 and Finger, 5 with increasing tension the 

 rhythmic contractions increase in force until one of them is sufficient 

 to overcome the resistance of the sphincter and to drive a little urine 

 into the urethra. The stimulus of this urine in the urethra starts the 

 whole reflex chain of events leading to micturition. The sphincter, by 

 the intermediation of the spinal centre, is inhibited. At the same time, 

 the longitudinal and circular fibres of the bladder wall contract, thus 

 emptying the bladder. The evacuation may be aided by an associated 

 contraction of the abdominal muscles. At the end of the act, the last 

 drops are expelled from the urethra by rhythmical contractions of the 

 perineal muscles, especially the accelerator urinse and levator ani. There 

 is no doubt that in this act the contraction of the ' detrusor ' (i.e. of 

 the whole bladder wall) is the most important factor in bringing 

 about the expulsion of the urine. Without the co-operation of the 

 bladder wall, the strongest contraction of the abdominal muscles is 

 inadequate to empty the bladder. It is much more uncertain what 

 part, if any, in the process, is played by the structures at the neck of the 

 bladder. Nearly all authorities lay a great stress on the importance of 

 a dilatation of the sphincter, either by the direct action of the detrusor 

 (longitudinal) fibres (Kohlrausch, 6 and Henle), or by an inhibition of the 



1 Arch, dephysiol. norm, etpath., Paris, 1896 (5), tome viii. p. 622. 



2 Bert, ibid.. 1869, tome iii. p. 650; S. Mayer, Hermann's " Handbuch, " Bd. v. (2), 

 8. 462. 



3 Arch./, d. ges. Physiol., Bonn, 1874, Bd. viii. S. 477. 



4 "Lehrbuch d. Pbysiologie." 



5 Allg. Wien. med. Ztg., 1893. 



u " Zur Anat. u. Physiol, der Beckenorgane," Leipzig, 1854, S. 14. 



