_a_, Sacrum. _b_, Coccyx. _c_, Tuberosity of ischium. _d_, Posterior or larger sacro-sciatic ligament. _e_, Anterior or small sacro-sciatic ligament, with the pudic nerve passing over its posterior aspect, and proceeding to the rectum and penis. _f_, Sphincter ani receiving its nervous supply from the pudic nerve. Portions of the muscles have been cut away, in order to show nerve filaments going to the mucous membrane, through the muscular fibers. _g_, Levator ani. _h_, Fat and areolar tissue occupying the ischiorectal fossa and covering the levator ani. _i_, Transverse muscles of perineum. _k_, Erector penis. _l_, Accelerator urinæ. 1, Pudic nerve. 2, Posterior sacral nerves proceeding to posterior part of the coccyx and to the sphincter ani. 3, Anterior sacral nerve (4th) supplying the sphincter ani. (Hilton.)] The orifice used for the elimination of undigested food and waste matter plays quite as important a part in the organic economy as the orifice that is employed for receiving food. Normal elimination, physiological and psychological, is the correlative process to prehension (seizure or appropriation), and the concord of the two forms the key-note of the organism. The muscles and tissues constituting the anal vent should be as flexible and responsive to the will or desire of the rectum for relief of its contents as the lips are in permitting the saliva to escape. In like manner the upper portion of the rectum (Figs. 6 and 8) should respond with instant readiness to the effort of the sigmoid flexure to expel its contents. But an abnormal condition like inflammation rooted in the anus and lower part of the rectum (Fig. 1, 4–4) will inhibit the passage of the pressing burden above them, which inhibition will cause the inflammation to extend to the sigmoid flexure, and thence on to the colon proper; and sooner or later the inflammation will penetrate the submucous coat (Fig. 1, 3–3), which is composed of fatty or areolar connective tissue in which trunks of nerves and blood-vessels are imbedded. The first symptom of inflammation is undue redness, followed by slight puffiness of the anal and rectal mucous membrane (Fig. 1, 4–4), with more or less sensitiveness of the tissues involved; and as its irritability increases there is more or less contraction of the muscular tissue forming the anus and rectum, which lessens the diameter of their bore. And the consequence of this contraction is of physiological concern to the victim, for in proportion to the contraction the normal demand of the victim for relief of the impending feces and gas is modified and lessened.