1292 



PHYSIOLOGY 



but is better known as the compressor urethra, 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. ganglion. 



Sup. mes. nerves 



Median mes. nerves 



Inf. mes. nerves 

 Inf. mes. ganglior 



Hypogastric nerves 



3rd lumh. vert. 



Hypogastric 



plexus 

 Sacrum 



Sciatic n. 

 ..Sacral nerves 



PIG. 537. Nerve supply to bladder of cat. (NAWUOCKI and SKABITSCHEWSKY.) 



of two kinds, one involuntary, the sphincter triyoni, 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 



