OF THE LOWER EXTREMITY. 403 



Fibular JRegion. Second Layer. 



Peroneus Longus. Flexor Accessorius. 



Peroneus Brevis. Lumbricales. 



F OT - Third Layer. 



Dorsal Region. 



T-, . TV ., Flexor Brevis Polhcis. 



Extensor Brevis Digitorum. Adductor Polliois. 



Plantar JRegion. Flexor Brevis Minimi Digiti. 



First Layer. Transversus Pedis. 



Abductor Pollicis F h L 



Flexor Brevis Digitorum. 



Abductor Minimi Digiti. The Interossei. 



ILIAC REGION. 

 Psoas Magnus. Psoas Parvus. Iliacus. 



Dissection. No detailed description is required for the dissection of these muscles. On the 

 removal of the viscera from the abdomen, they are exposed, covered by the peritoneum and a 

 thin layer of fascia, the fascia iliaca. 



The iliac fascia is the aponeurotic layer which lines the back part of the 

 abdominal cavity, and incloses the Psoas and Iliacus muscles throughout their 

 whole extent. It is thin above; and becomes gradually thicker below, as it 

 approaches the femoral arch. 



The portion investing the Psoas is attached, above, to the ligamentum arcua- 

 tum internum ; internally, to the sacrum ; and 'by a series of arched processes 

 to the intervertebral substances, and prominent margins of the bodies of the 

 vertebrae ; the intervals so left, opposite the constricted portions of the bodies, 

 transmitting the lumbar arteries and filaments of the sympathetic nerve. Ex- 

 ternally, this portion of the iliac fascia is continuous with the fascia lumborum. 



The portion investing the Iliacus is connected, externally, to the whole length 

 of the inner border of the crest of the ilium ; and internally, to the brim of 

 the true pelvis, where it is continuous with the periosteum, and receives the 

 tendon of insertion of the Psoas Parvus, when that muscle exists. External 

 to the femoral vessels, this fascia is intimately connected with Poupart's liga- 

 ment, and is continuous with the fascia transversalis ; but, as the femoral ves- 

 sels pass down into the thigh, it is prolonged down behind them, forming the 

 posterior wall of the femoral sheath. Under the femoral sheath, the iliac fascia 

 surrounds the Psoas and Iliacus muscles to their termination, and becomes con- 

 tinuous with the iliac portion of the fascia lata. Internal to the femoral ves- 

 sels, the iliac fascia is connected with the ilio-pectineal line, and is continuous 

 with the pubic portion of the fascia lata. The iliac vessels lie in front of the 

 iliac fascia, but all the branches of the lumbar plexus behind it ; it is separated 

 from the peritoneum by a quantity of loose areolar tissue. In abscess accom- 

 panying caries of the lower part of the spine, the matter makes its way to the 

 femoral arch, distending the sheath of the Psoas ; and when it accumulates in 

 considerable quantity, this muscle becomes absorbed, and the nervous cords 

 contained in it are dissected out, and lie exposed in the cavity of the abscess ; 

 the femoral vessels, however, remain intact, and the peritoneum seldom becomes 

 implicated. 



(Remove this fascia, and the muscles of the iliac region will be exposed.) 



The Psoas Magnus (Fig. 254) is a long fusiform muscle, placed on the side of 

 the lumbar region of the spine and margin of the pelvis. It arises from the 

 sides of the bodies, from the corresponding intervertebral substances, and from 

 the front of the bases of the transverse processes of the last dorsal and all the 

 lumbar vertebrae. The muscle is connected to the bodies of the vertebras by 

 five slips ; e.ach slip is attached to the upper and lower margins of two vertebras, 



