392 



THE EXCRETIONS OF THE BODY 



duce the desire to empty the bladder; hence the doctrine that this desire 

 is due to the escape of the urine into the urethra is not correct (Guyon). 

 The flow of urine can be suppressed by voluntary contraction of the outer 

 sphincter (probably also of the inner). 



Micturition results from a voluntary relaxation of the external sphincter, 

 whereupon the reflex contraction of the whole musculature of the bladder, 



Nerves to 



coeliac Sympathetic 

 axis nerves 



Superior 



mesenteric 



ganglion 



Connecting 

 strands 



Superior 

 mesenteric nerve 



Med. mes. nerve 



Inf. mes. nerve ~ - - _ 



Nerve to mes. 

 artery 

 Inf. mes. gang. ^ /y 



Hypogastric 

 nerves 



Rectum / 



Bladder 



Femur -- 



Ischium 



Urethra 



III. Lumbar 

 vertebra 



Ramus 

 communicans 



IV. Lumb. vert. 



" V. Lumb. vert. 



) Rami 



communicantes 



VI. Lumb. vert. 



-H-r-t VII. Lumb. vert. 



Vesical plexus 



FIG. 145. The nerves of the bladder, after Nawrocki and Skabitschewsky. 



including that of the internal sphincter, follows. A large part of the longi- 

 tudinal fibers pass over without interruption into the fibers of the sphincter 

 an arrangement which insures the dilatation of the opening. (Rehfisch advo- 

 cates the view that the internal sphincter also relaxes when the passage is 

 opened.) Micturition is aided by the bulbo-cavernosus muscle, in that it 

 compresses the bulbous urethne, thus expelling the contents of the latter. Ab- 



