1292 PHYSIOLOGY 



but is better known as the compressor urethrce, forms a flat ring around 

 the second part of the urethra, extending in the male from the prostate 

 to the bulb, where its function is taken up by the bulbo-cavernosus. 



The bladder is therefore supplied with a powerful muscular wall, 

 the contraction of which will cause its evacuation, and with sphincters 



Sup. mes. ganglior. 



Sup. mes. nerves 



Median mes. nerves 



Inf. mes. nerve: 



Inf. mes. ganglior 



Hypogastric nerves 



Rectum 



Bladde. 



Femu;-- 



Ischiun 

 Urethra 



3rd lumb. vert. 



--Hypogastric 



plexus 

 Sacrum 



-Sciatic n. 

 ..Sacral nerves 



FIG. 537. Nerve supply to bladder of cat. (NAWEOCKi and SKABITSCHEWSKY.) 



of two kinds, one involuntary, the sphincter trigoni, at the upper neck 

 of the bladder, and the voluntary, the sphincter urogenitalis and bulbo- 

 cavernosus muscles, which can empty the lower parts of the urethra. 



The nerve-supply of the bladder (Fig. 537) is derived from two main 

 sources, namely, from the upper four lumbar nerves through the sympa- 

 thetic system, and from the second and third sacral nerves by means of 

 the pelvic visceral nerves or nervi erigentes. The upper lumbar nerves 



