284 THE INFERIOR EXTREMITY 



the twigs from adjacent nerves cross one another and sometimes 

 unite with one another. Trace such twigs to their sources of 

 origin ; when the trunk from which they arise is found, follow 

 it and its branches to their peripheral distribution. If the plan 

 outlined is followed the dissector will demonstrate the branches 

 of the lumbar nerves without any great difficulty. He should 

 then attempt to find the lateral branches of the ilio-hypogastric 

 and last thoracic nerves, following the same plan of search. 

 The trunks of the two branches cross the iliac crest anterior to 

 the lumbar nerves, the lateral branch of the last thoracic about 

 5 cm. posterior to the anterior superior spine of the ilium and 

 the lateral branch of the ilio-hypogastric a centimetre or more 

 further back. If the branches of the posterior division of the 

 lateral cutaneous nerve of the thigh were found and left in 

 position when the anterior part of the thigh was dissected, they 

 may be revised now, otherwise the dissector need waste no time 

 in looking for them, for they will have been already removed. 

 No time need be lost in looking for the perforating cutaneous 

 nerve. It pierces the deep fascia and enters the superficial fascia 

 near the medial part of the lower border of the glutseus maximus 

 about 2 or 3 cm. from the tip of the coccyx and medial to the 

 ischial tuberosity, and it has either been displayed and left in 

 situ by the dissector of the perineum, or it has been removed. 

 To display the gluteal branches of the posterior cutaneous nerve 

 of the thigh, cut through the superficial fascia along the lower 

 border of the glutaeus maximus till the deep fascia is exposed, 

 then reflect the superficial fascia upwards and secure the branches 

 sought for as they pierce the deep fascia about midway between 

 the trochanter major and the tuber ischii. 



In well-injected subjects many of the nerves mentioned are 

 accompanied by small injected arteries which serve as guides 

 to the nerves, but such arteries cannot be depended upon, and 

 the dissector should rely upon his senses of sight and touch to 

 enable him to distinguish the firmer nerve fibres from the strands 

 of connective tissue which permeate the fat. 



After the cutaneous nerves have been demonstrated the 

 remains of the superficial must be removed both from the 

 region of the glutaeus maximus and the region anterior to it in 

 order that the deep fascia may be examined. 



Deep Fascia. The deep fascia now exposed differs in 

 character in the anterior and posterior pans of its extent. 

 In front of the glutaeus maximus, where the fascia lies over the 

 anterior part of the glutaeus medius, it is dense in texture 

 and opaque and pearly white in colour. That part stands 

 in marked contrast with the deep fascia over the glutaeus 

 maximus itself, which is thin and transparent. Subsequent dis- 

 section will show that the dense fascia over the anterior part 

 of the glutaeus medius, when it reaches the anterior border 

 of the glutaeus maximus, splits into two lamellae which 

 enclose the glutaeus maximus between them. 



Dissection. Follow the branches of the posterior cutaneous 



