THE INHIBITOR Y NER VES 7 1 



ergotoxin stimulation or adrenalin will produce inhibition, not 

 contraction. By this means the presence of inhibitory nerves 

 has been detected in many cases. The presence of inhibitory 

 nerves to the musculature of the uterus has thus been demon- 

 strated by Dale, who has shown that they pass to the uterus 

 along the hypogastric nerves, having passed out of the spinal 

 cord in the lumbar splanchnics. He has shown that in the 

 virgin uterus of certain animals inhibition is the normal effect 

 of either stimulating the hypogastric nerve or of giving adrenalin, 

 while in the pregnant uterus the normal effect is contraction, 

 which can then be converted into inhibition by paralysing the 

 motor fibres with ergotoxin. The motor and inhibitory neurons 

 for the uterus have therefore travelled out together, and are 

 both found in the groups of cells situated in the neighbourhood 

 of the uterus. 



In the urodermal group we have also especially to consider 

 the ureters, in which similar groups of nerve cells have been des- 

 cribed by Protopopow. The connector fibres to these nerve cells 

 run in the hypogastric nerves, and Fagge has shown that stimu- 

 lation of the hypogastric nerve in the dog is always followed by 

 a motor effect on the ureter, which is evidenced either by a quicken- 

 ing of the normal rhythm of contraction, by the production of 

 groups instead of single contractions, or by the production of 

 groups of contractions in a previously quiescent ureter. Elliott 

 has given evidence of an inhibitory action on the muscles of the 

 ureter in the dog upon the application to the ureter of adrenalin, 

 I in 2000. Neither the uterus nor the ureter is innervated in 

 any degree from the sacral outflow. 



I conclude that both the inhibitory and motor nerve cells of 

 the urogenito-dermal system have travelled out together in the 

 thoracico-lumbar outflow right up into the organs themselves, 

 and their connector fibres reach these cells by way of the lumbar 

 splanchnics and the hypogastric nerves. 



We come finally to the most interesting group, the sphincter 

 or sympathetic musculature of the gut, and with it we will con- 

 sider also the inhibitory fibres for the sacral and bulbar endo- 

 dermal musculature. 



In the sphincter musculature of the cloacal region of the gut I 

 have included the internal sphincter ani and the sphincter of the 

 bladder and urethral muscles. The motor nerve cells for all 



