406 DISSECTION OF THE ABDOMEN. 



The deeper layer (aponeurosis of the fascia lata, Scarpa) is thinner and 

 more membranous than the other, and is closely united to the tendon of 

 the external oblique by fibrous bands, especially towards the linea alba. 

 Like the subcutaneous part, this layer is continued upwards on the abdo- 

 men, and inwards to the penis and the scrotum : here it becomes very 

 thin, and reaches the perinaeum, where it has attachments to the subjacent 

 parts, as before specified (p. 393). Towards the limb, it ends a little be- 

 low Poupart's ligament in the fascia lata across the front of the thigh ; as 

 it passes over the ligament it is closely joined to that band by fibrous 

 tissue. 



Urine effused in the perinaeum from rupture of the urethra will be 

 directed through the scrotum and along the spermatic cord to the abdo- 

 men (p. 393). From the arrangement of the deeper layer of the fascia 

 across the thigh, it is evident that the fluid cannot pass down the limb, 

 though its progress over the front of the abdomen is uninterrupted. 



In the female the fatty layer of the groin is separable into two layers, 

 and the disposition of each is nearly the same as in the male ; but the 

 part that is continued to the scrotum in the one sex enters the labium in 

 the other. In the female the round ligament of the uterus is lost in it. 



CUTANEOUS NERVES. The nerves in the teguments are derived from 

 the trunks of the lower intercostal nerves ; thus the cutaneous branches, 

 along the side of the belly, are offsets from five or six of those nerves ; 

 and the cutaneous branches, along the front, are the terminal parts of the 

 same trunks. Two other cutaneous offsets from the lumbar plexus, viz., 

 ilio-hypogastric and ilio-inguinal, appear at the lower part of the ab- 

 domen. 



The lateral cutaneous nerves of the abdomen emerge between the digi- 

 tations of the external oblique muscle, in a line with the same set of nerves 

 on the thorax ; and the lowest are the most posterior. As soon as they 

 reach the surface they divide, with the exception of the last, into an an- 

 terior and a posterior branch : 



The posterior branches are small in size, and are directed back to the 

 integuments over the latissimus dorsi muscle. 



The anterior branches are continued nearly to the edge of the rectus 

 muscle, and in increasing in size from above down, supply the integu- 

 ments on the side of the belly ; they furnish offsets to the digitations of 

 the external oblique muscle. 



The lateral cutaneous branch of the last dorsal nerve is larger than 

 the rest, and does not divide like the others. After piercing the fibres of 

 the external oblique muscle, it is directed over the iliac crest to the sur- 

 face of the gluteal region. 



The anterior cutaneous nerves of the abdomen pierce the sheath of the 

 rectus: in the integuments they bend outwards towards the lateral cuta- 

 neous nerves. The number, and the situation of these small nerves, are 

 very uncertain. 



The ilio-hypogastric nerve is distributed by two pieces : one passes 

 over the crista ilii (iliac branch), the other ramifies on the lower part of 

 the abdomen (hypogastric branch): 



The iliac branch lies close to the crest of the hip bone near the last 

 dorsal nerve, and enters the teguments of the gluteal region. 



The hypof/astric branch pierces the aponeurosis of the external oblique 

 muscle above the abdominal ring, and is distributed, as the name ex- 

 presses, to the lower part of the abdomen. 



