372 PHYSIOLOGY CHAP. 



tion of the sympathetic ranii sometimes produces a brief contraction, 

 but as its principal effect causes inhibition of all the movements 

 of the last part of the gut. The action of the sacral and sympa- 

 thetic fibres on the colon, rectum, and anus would thus be analogous 

 to that exerted by the vagus and splanchnics on the rest of the 

 stomach and intestines. It is an open question, left for further 

 investigation to decide. 



The tonic contraction habitual to the sphincters of the anus is 

 due, in part at least, to the action of a nervous centre situated in 

 the lumbar segment of the cord. According to Budge and Masius 

 (1868) this ano-spinal centre is localised in dogs in the tract 

 corresponding with the level of the fifth lumbar vertebra, in 

 rabbits, on the other hand, in the tract between the sixth and 

 seventh lumbar vertebrae. If in these animals the cord be 

 divided below the ano-spinal centre, or if in rabbits the abdominal 

 aorta be compressed for a long period (Gaglio), relaxation of the 

 sphincters follows. If, on the contrary, the cord be cut above 

 the level of this centre, the sphincters regain their normal 

 tonicity as soon as the inhibitory effect of the operation has 

 passed off. 



More recently, however, Goltz and Ewald (1895) observed 

 in dogs deprived of the whole of the lumbar-sacral cord that the 

 phenomenon of incontinence of faeces disappears after some months, 

 and the anal sphincters regain their normal function. The sympa- 

 thetic ganglia can thus regulate the tone of the sphincters inde- 

 pendently of the ano-spinal centre. In fact, after the destruction 

 of the spinal centre, Courtade and Guyon (189*7), and subsequently 

 Frankl-Hochwart (1900), saw that centripetal excitation of the' 

 hypogastric rami, which give off sensory fibres to the ano-rectal 

 mucous membrane, can produce reflex contraction of the sphincters. 

 The reflex ceases after destruction of the inferior niesenteric 

 plexus. The central station of the reflex therefore lies in this 

 plexus, since all relation of the latter with the spinal centre has 

 previously been abolished. 



The sphincters are also capable, after some months, of regaining 

 their natural tone, when the whole of the nerves that supply the 

 rectum and the anal sphincters have been completely occluded, 

 along with the central action of all the extra-rectal sympathetic 

 ganglia. This was established for dogs by Arloing and Chautre 

 (1897-98) by repeated experiments. This fact can only be explained 

 by admitting that the intra-rectal peripheral ganglia of Auerbach's 

 plexus can exercise a reflex tonic action upon the sphincters, 

 independent of the connections with the extra-intestinal nervous 

 system. 



We must therefore conclude that in cases of incontinence of 

 faeces of central origin there is, along with the depression of the 

 tonic action of the ano-spinal centre, also a functional inhibition 



