Fig. 2.
a, Ulcer on sphincter ani. b, Filaments of two nerves are exposed on the ulcer, the one a nerve of sensation, the other of motion, both attached to the spinal marrow, thus constituting an excito-motory apparatus. c, Levator ani. d, Transversus perinei. (Hilton.)
There are other exciting causes of proctitis, but, since they are exceptional when compared with the neglected diaper, we need not concern ourselves with them at present.
The muscular coat of the rectum consists of two layers: an inner circular and an outer longitudinal band. The inner circular layer of muscular tissue of the rectum forms the internal sphincter muscle; and the outer longitudinal bands merge with those of the external sphincter. The anal orifice is closed or guarded by two strong sphincter muscles, as shown in Figs. [1], 2, and 3. These muscles are abundantly supplied with nerves, of which branches are distributed to the bladder and other adjacent organs, which accounts for the sympathy of these organs and their grave disturbance when disease inheres in the anus and rectum.
Fig. 3.
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.