THIGH AND LEG. 



337 



and fasciae covering the inlet. The fossa extends in an upward direction to the 

 pubic bone ; in a backward direction to the sacrum, forming the anterior and 

 posterior recesses of Morris. In liberating pus in this fossa, cut through the base ; 

 then lay your knife aside and continue the operation with a blunt instrument. 



1. Give tlie shape of, and tell ivJiat yon mean by, the pelvic outlet. 



It is lozenge-shaped, and is the space bounded by the pubic arch above, the 

 coccyx below, and the greater sacro-sciatic ligament, tuberosity of the ischium, 

 and ischio-pubic ramus laterally. 



2. Give the subdivisions of this space, and tell zvhere the boundary -line between 

 the two is located. 



A line from tuberosity to tuberosity of the ischium divides the space into an 

 anterior triangle, the perineum, and a posterior triangle, the ischio-rectal fossa. 



P'IG. 234. MUSCLE OF GUTHRIE. 

 I. Bulbo-cavernosus (accelerator urinre) muscle. 

 2. Muscle of Guthrie (transversus perinaei profun- 

 dus). 3. Superficial transverse muscle. 4. Ex- 

 ternal sphincter ani. 5. Levator ani. 



FIG. 235. MUSCLE OF GUTHRIE AND WILSON. 



i. Bulb of urethra. 2, 2. Muscle of Guthrie 

 (transversus perinsei profundus). 3. Muscle of 

 Wilson. 4. Transversus perin<iei superficialis. 

 5. External sphincter ani. 6. Levator ani. 



3. Give the contents of the ischio-rectal fossa. 



It contains the rectum and the fossa on each side of the rectum, called ischio- 

 rectal fossa. 



4. Give the geometrical parts of this fossa and the importance you attach to 

 each part. 



(i) Apex, at the white line, the origin of the levator ani ; (2) base, the skin 

 and fasciae, between anus and tuber of ischium ; (3) outer wall, the obturator 

 internus, Alcock's canal and contents ; (4) inner wall, the levator ani and coccy- 

 geus muscles covered by the anal fascia ; (5) an anterior or pubic recess ; (6) a 

 posterior or sacral recess. 



5. Where is Alcock's canal, how is it found, and what are its contents ? 



It is in the outer wall of the ^chic-rectal fossa, in a delamination of the ob- 

 turator fascia ; it contains the internal pudic vessels and nerve and extends from 

 the lesser sacro-sciatic foramen to the deep triangular ligament. 



6. Name the contents of the ischio-rectal fossa. 



The fossa contains fat and connective tissue, in which are embedded the 

 inferior haemorrhoidal nerves and vessels. On dissection you will see these 

 structures crossing the fossa to supply the rectum. 



