. A manual of diseases of the nervous system. the process, butcannot control it. It is often said that there is permanent relaxationof the sphincters, but this is true only when the lumbar centres areinactive or destroyed. In this condition evacuation occurs as soonas faeces or urine enter the bowel or rectum. The urine escaj^escontinuously, instead of being expelled at intervals. The condition isless obvious in the case of the rectum, because there is no such con-tinuous passage of faeces into the rectum as there is of urine into thebladder. We may, however, distinguish between the two states
. A manual of diseases of the nervous system. the process, butcannot control it. It is often said that there is permanent relaxationof the sphincters, but this is true only when the lumbar centres areinactive or destroyed. In this condition evacuation occurs as soonas faeces or urine enter the bowel or rectum. The urine escaj^escontinuously, instead of being expelled at intervals. The condition isless obvious in the case of the rectum, because there is no such con-tinuous passage of faeces into the rectum as there is of urine into thebladder. We may, however, distinguish between the two states of therectum by the introduction of the finger. If the lumbar centre isinactive, there is a momentary contraction, due to local stimulation ofthe sphincter, and then permanent relaxation. If, however, the reflexcentre and motor nerves from it are intact, the introduction of thefingei is followed, first by relaxation, and then by gentle, firm, toniocontraction. I have verified this by introducing an india-rubber 3IQ I II II liiii! Ill IB! E. Fig-. 85.—Teacings of the Action op the Sphincteb Ani. The vertical lines represent seconds of on contraction of sphincter of the injection into the rectum of a smallquantity of air at *. a, fall in pressure due to the inhibition of the contrac-tion; J, rise due to the slowly returning contraction. 2. Effect of the intro-duction of the instrument, a, sudden rise of lever at moment of introduction,due to the exposure of the instrument to the pressure of the sphincter (the topof this line represents the deo^ree of previous contraction); 5, initial rise due toincreased contraction; c, fall from partial inhibition; d, subsequent contrac-tion, rising to a greater degree than the initial contraction, iimi subsequentlyfalling slifjlitly. 3. Effect of cough, a, pressure of tonic contraction ofspliiucter (the slight irregularities are due to pulse-waves); h, fall in pressure,due to the movement of the instrument by the cough; c, initia
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