Human physiology . tion already discussedin Chapter IV. (p. 265 et seq.) as tothe simultaneous or alternate action ,> ., , ,. •, . •, FIG. 106.—Schema of nerves which arise (in OI the longitudinal Or Circular dog) from last part of lumbar cord, and fibres of the small intestine, comesup again in relation to themuscles of the colon and experimenters (Courtade and Guyon, 1897) stated that electrical stimulation of thesympathetic rami in the dog produces contraction of the circularfibres of the colon, rectum, and anus, and inhibits the contractionof the longitudinal fibres ; vic
Human physiology . tion already discussedin Chapter IV. (p. 265 et seq.) as tothe simultaneous or alternate action ,> ., , ,. •, . •, FIG. 106.—Schema of nerves which arise (in OI the longitudinal Or Circular dog) from last part of lumbar cord, and fibres of the small intestine, comesup again in relation to themuscles of the colon and experimenters (Courtade and Guyon, 1897) stated that electrical stimulation of thesympathetic rami in the dog produces contraction of the circularfibres of the colon, rectum, and anus, and inhibits the contractionof the longitudinal fibres ; vice versa, stimulation of the sacr/t/nerves contracts the longitudinal and inhibits the circular fibres,including those of the sphincter. There would thus be a functionalantagonism between the two orders of nerves. On the otherhand, Langley and Anderson (1895-96), experimenting on therabbit, state that stimulation of the sacral nerves throws bothlongitudinal and circular muscles into contraction, while stimula-. — Ce. in sacral cord. (Frangois-Franck.) Sa,os sacrum ; 5L, GL, 7L, lumbar vertebrae ;, sciatic nerve ; 2V. c, nervous erigensfrom 1 and 2 sacral uerves(J5, :.>) : A, y,nervous pudendus ; C. e, cauda equina. 372 PHYSIOLOGY CHAP. tion of the sympathetic ranii sometimes produces a brief contraction,but as its principal effect causes inhibition of all the movementsof the last part of the gut. The action of the sacral and sympa-thetic fibres on the colon, rectum, and anus would thus be analogousto that exerted by the vagus and splanchnics on the rest of thestomach and intestines. It is an open question, left for furtherinvestigation to decide. The tonic contraction habitual to the sphincters of the anus isdue, in part at least, to the action of a nervous centre situated inthe lumbar segment of the cord. According to Budge and Masius(1868) this ano-spinal centre is localised in dogs in the tractcorresponding with the level of the fifth lumbar vertebra, inrabbits
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