DISSECTION OF THE LOWER EXTREMITY 125 



(e) Cutaneous twigs from the posterior cutaneous nerve of the thigh 



(N. cutaneus femoris posterior) (O. T. cutaneous 

 branches of small sciatic), passing around the lower 

 border of the glutaeus maximus. 



(ea) Inferior nerves of buttock (Nn. clunium inferior es}. 



(eb) Perineal branches (rami perineales). 



(f) Posterior branches of lateral cutaneous nerve of thigh (N. cuta- 



neus femoris lateralis) (0. T. external cutaneous). 



These nerves should be traced as far as possible and their 

 distribution carefully noted. 



Deep Fascia. 



Remove the remaining portion of the superficial fascia, pre- 

 serving the nerves, and expose the deep fascia. 



Notice the general character of this fascia anteriorly, where 

 it covers the M. glutaeus medius, and compare it in general 

 characteristics with that portion of the fascia covering the 

 M. glutaeus maximus. After having made a careful study of 

 this fascia, remove it in a continuous layer from above down- 

 ward, after having rendered the muscle tense beneath by ro- 

 tating the thigh medial ward. The borders of the muscle should 

 be carefully defined; note that the thin fascia covering the 

 latter becomes continuous with the dense pearly aponeurosis 

 covering the muscle immediately anterior to it. In dissecting 

 away this fascia, cut always in the direction of the muscle fibres. 



Glutaeus Maximus Muscle (M. glutaeus maximus). 



Note carefully the form, position, origin, insertion, action, 

 and innervation of this muscle. What is the relation of the 

 muscle to the dense fibrous band (tractus iliotibialis) passing 

 from the ilium to the tibia? How does the size of this muscle in 

 man compare with that in other animals? After having care- 

 fully examined and drawn this muscle, the student may reflect 

 it in the following manner : The two borders of the muscle should 

 be freed and the hand passed under the muscular mass. Detach 

 the muscle from its attachment to the ilium. Proceed cautiously 

 as the upper margin of the greater sacrosciatic foramen (fora- 

 men ischiadicum ma jus) is approached and avoid the gluteal ves- 

 sels as they pass through this opening. Secure these and detach 

 the muscle from the side of the sacrum, exposing the piriform 

 muscle (M. piriformis) as it emerges from the pelvis. Separate 

 the muscular fibres from the ligamentum sacrotuberosum (0. T. 

 great sacrosciatic ligament) and the side of the coccyx, avoiding 



