ANATOMY OF THE ABDOMEN, ETC. 



of two muscles which have their insertions outside ; thes< 

 are the obturator interims and the pyriformis. 



The OBTURATOR INTERNUS MUSCLE arises from the bon< 

 around the obturator foramen, and from the membran< 

 which stretches across it ; it forms a triangular belly, 

 covered b}^ the pelvic fascia, which, tapering to a point, 

 passes out of the lesser sacro-ischiatic foramen, to be in- 

 serted into the digital fossa of the trochanter major. 



The PYRIFORMIS MUSCLE arises from the sacrum, between 

 the first and fourth anterior sacral foramina, from the 

 greater sacro-ischiatic ligament, and from a portion of the 

 ilium, forming a triangular belly which terminates in a 

 rounded tendon, and passing out at the sacro-ischiatic 

 foramen, is inserted into the digital fossa of the trochanter 

 major. 



The COCCYGEUS MUSCLE is a small collection of muscular 

 and tendinous fibres, arising from the spine of the ischium, 

 and from the lesser sacro-ischiatic ligament, and inserted 

 into the side of the coccyx ; its lower border is connected 

 with the levator ani. It is apt to be mutilated in the re- 

 moval of the rectum and anus. 



DISSECTION VII. 



1 THE RECTUM. 



The pelvic viscera may now be examined, commencing with the 

 rectum ; this should be cleared from all extraneous tissue, but with- 

 out separating it from its connections with the bladder. 



The RECTUM is about eight inches in length ; it follows 

 a curved direction, corresponding to that of the sacrum, 

 and gradually increases in size, especially in old people, 

 from its commencement to within an inch and a halfLof the 

 anus. The last inch and a half is contracted, and follows 

 a direction downward and backward to its termination in 

 the anus. Its anterior surface is in contact with the 

 bladder and its appendages in the male, and the uterus 

 and vagina in the female, the upper portion being separated 

 only by the recto-vesical, or recto-uterine fold of the peri- 

 toneum, while the lower portion is in direct apposition with 

 the bladder, or separated from it only by cellular tissue. 

 The rectum, laid open along its posterior aspect, dis- 



