777 K MTHVLKN AND FASCIA 



I. Muscles of the Ischio-rectal Region. 



Corrugator cutis ani. Internal sphincter ani. 



External sphincter ani. Leva-tor ani. 



Coccygeus. 



The Corrugator Cutis Ani. Around the anus is a thin stratum of involuntary 

 muscular fibre, which radiates from the orifice. Internally, the fibres fade off 

 into the subinucous tissue, while externally they blend with the true skin. By 

 its contraction it raises the skin into ridges around the margin of the anus. 



The External sphincter ani is a thin, flat plane of muscular fibres, elliptical in 

 shape and intimately adherent to the integument surrounding the margin of the 

 anus. It measures about three or four inches in length from its anterior to its 

 posterior extremity, being about an inch in breadth opposite the anus. It arises 

 from the tip and back of the coccyx by a narrow tendinous band, and from the 

 superficial fascia in front of that bone; and is inserted into the central tendinous 

 point of the perinneum, joining with the Transversus perinsei, the Levator ani, 

 and the Accelerator urinse. Like other sphincter muscles, it consists of two 

 planes of muscular fibre, which surround the margin of the anus and join in a 

 commissure in front and behind, some fibres crossing from side to side in front 

 and behind the anus. 



PECTINEUS. 

 ADDUCTOR - 



LONGUS. 

 GRACILIS. 



Epididymis. 



Ampulla. 



Ampulla of rasa 

 deferent. 



Testicle. 



Ascending ramus of 



ISCH1UM. , 



Internal pudic 

 vessels and nerve. 



FIG. 222. Side view of pelvis, showing Levator ani. (From a preparation in the Museum of the Royal 

 College of Surgeons.) 



Nerve-supply. A branch from the anterior division of the fourth sacral and 

 the inferior haemorrhoidal branch of the internal pudic. 



Actions. The action of this muscle is peculiar: 1. It is, like other muscles, 

 always in a state of tonic contraction, and having no antagonistic muscle, it keeps 

 the anal orifice closed. 2. It can be put into a condition of greater contraction 

 under the influence of the will, so as to occlude more firmly the anal aperture in 

 expiratory efforts unconnected with defecation. 3. Taking its fixed point at 

 the coccyx, it helps to fix the central point of the perinseum, so that the Accele- 

 rator urinae may act from this fixed point. 



The Internal sphincter ani is a muscular ring which surrounds the lower 



