THE PIGEON. 247 



XLVI. Dissect away the remains of all the organs still 

 left in the body cavity, and make out on its 

 dorsal wall : 



291. The thoracic spinal nerves, emerging from the 

 intervertebral foramina of the thoracic vertebra, and passing 

 transversely outwards parallel to and equidistant from the 

 ribs. 



292. The brachial plexus, a network of nerves at 

 the root of the neck, formed by the union of the posterior 

 cervical and anterior thoracic spinal nerves : from it are 

 given off the nerves to the shoulder and wings. 



293. The lumbar plexus, formed by the nerves which 

 emerge through the intervertebral foramina of the lumbar 

 vertebra : it gives off the femoral nerve to the front of 

 the thigh, and the small obturator nerve which traverses 

 the obturator fissure (§ 105) and goes to the muscles about 

 the acetabulum. 



294. The sciatic plexus, formed by nerves emerging 

 from the intervertebral foramina of the sacral vertebrae : 

 it goes mainly to form the great sciatic nerve which 

 accompanies the sciatic artery {§ 224). 



295. The sympathetic nerves, delicate, paired, longi- 

 tudinal cords, running close alongside the vertebral column, 

 and having at intervals ganglia, which are connected with 

 the spinal nerves just at their exit from the intervertebral 

 foramina. 



Posterioi-ly the two sympathetics unite in a single small ganglion 

 impar • anteriorly each forms a large posterior cervical ganglion 

 lying ventral to the brachial plexus, and thence passes along the verte- 

 brarterial canal, alongside the vertebral artery, to the head. 



XLVII. Dissect away the skin from the dorsal surface 

 of the uropygium, and note : 



296. The uropygial gland, a whitish, bilobed organ. 



