84 ANATOMY. 



Internal Sphincter, a wuscula* ring, half an inch broad, about an inch from 

 the margin of the anus; is an aggregation of the involuntary circular fibres 

 or the intestine. 



FIG. 43. 



Sphincter Tertius of Hyrtl, from the sacrum, encircling the rectum about 4 



inches above the anal orifice. [Demonstrated by Hyrtl, Nelaton, and Vel- 



peau, but denied by most anatomists.] 

 Accelerator Urinse, 1 from the central tendon of the perineum and the median 



raphe in front, fibres spread over the bulb, corpus spongiosum, corpus 



cavernosum, 17 and dorsal vessels. Action, to accelerate the flow of urine, 



and erect the penis. Nerve, perineal branch of pudic. 

 Erector Penis, 2 from the inner surface of the tuberosity of the ischium, the 



crus penis, and pubic ramus, into the crus penis laterally and inferiorly. 



Action, to maintain erection. Nerve, perineal. 

 Transversus Perinei, 3 from the ascending ramus of the ischium, into the 



central tendon of the perineum. Action, to draw tense the central tendon. 



Nerve, perineal. 

 Levator &ri\p from the body and ramus of the pubes posteriorly, pelvic fascia, 



and the spine of the ischium, into the tendinous centre of the perineum, 



sides of the rectum (and vagina), apex of the coccyx, and a fibrous raphe 



extending from the coccyx to the anus. Action, to support the lower end of 



the rectum and vagina and the bladder, and assist in forming the floor of the 



pelvis. Nerves, inferior hemorrhoidal and 4th sacral. 

 Compressor Urethrae, from the upper part of the ramus of the pubes, into 



its fellow of the opposite side after encircling the membranous portion of th 



urethra. Action, stop-cock muscle. Nerve, perineal. 



