=M. levator ani= (or =pubiocaudalis=) (Fig. 162, 11).--This muscle lies in the pelvic cavity. Each muscle forms a nearly vertical sheet, and between the two are the rectum and the urethra.
_Origin_ from the symphysis of the pelvis.
_Insertion_ into the midventral line of the centra of the third, fourth, and fifth caudal vertebræ, close to the muscle of the opposite side. This muscle is frequently continuous with the iliocaudalis (Fig. 162, 11′).
_Action._--Bends the tail and compresses the rectum.
=M. ischiocavernosus= (Fig. 113, _m_; Fig. 114, _e_).--A small, flat, spindle-shaped muscle which lies upon the crus of the penis or clitoris. Each has
_Origin_ from the caudal border of the ramus of the ischium, about one centimeter from the median line.
_Insertion_, in the male, into the whole outer surface of the crus penis, or bulb of the corpus cavernosum penis. In the female the muscle is smaller than in the male, and the insertion is into the ventral surface of the urogenital sinus, at the base of the clitoris.
=M. transversus perinei= (Fig. 114, _i_).--A small bundle of fibres which arises from the medial surface of the ischium, just dorsad of the origin of the ischiocavernosus, and passes mediad to join the sphincter ani internus (_c_).
=M. caudoanalis= (S.-D.) (Fig. 113, _f_; Fig. 114, _g_).--A slender, flat bundle of fibres having origin on the middle line of the ventral surface of the second and third caudal vertebræ. It passes caudoventrad, lying between the levator ani and the caudorectal (Fig. 113, _e_; Fig. 114, _j_), and unites with the ventral portion of the sphincter ani internus (Fig. 113, _h_).
[Illustration: FIG. 113.--MUSCLES OF THE ANUS, UROGENITAL ORGANS, AND TAIL IN THE MALE (SLIGHTLY SCHEMATIC).
One side of the pelvis has been removed, _a_, _a′_, M. extensor caudæ lateralis; _b_, M. abductor caudæ externus; _c_, _c′_, M. flexor caudæ longus; _d_, M. flexor caudæ brevis; _e_, M. caudorectalis; _f_, M. caudoanalis; _g_, M. caudocavernosus; _h_, M. sphincter ani internus; _i_, M. sphincter ani externus; _j_, M. levator scroti; _k_, M. rectocavernosus; _l_, M. bulbocavernosus; _m_, M. ischiocavernosus (cut); _n_, M. compressor urethræ membranaceæ. 1, tail; 2, rectum; 3, bulbourethral or Cowper’s gland; 4, prostate gland; 5, symphysis pubis; 6, penis; 7, glans penis; 8, testis; 9, spermatic cord.]