THE PIGEON 183 



Find the main sympathetic nerves of the trunk. In the anterior 

 and middle portions of the trunk the main nerve cords lie in the 

 abdominal cavity along the base of the ribs. They consist here 

 of two longitudinal nerves on each side, which meet in the spinal 

 ganglia, the sympathetic ganglia and the spinal ganglia being fused. 

 Note carefully the relation of these two nerves to the ribs. At the 

 base of the brachial plexus are two unusually large ganglia. 



Follow the nerves and the ganglia into the posterior portion of 

 the abdominal cavity. The ganglia will be seen to become rapidly 

 smaller, and in the caudal region they are wanting. The double 

 sympathetic nerve extends between the brachial and the lumbar 

 plexus, posterior to which a single strand is present on each side 

 of the spinal column. 



A network of nerves starting from the longitudinal sympathetic 

 nerves and ganglia in the anterior portion of the body cavity is 

 present, from which the large splanchnic nerve springs. This nerve 

 passes medially and joins the solar plexus, a network of nerves 

 and ganglia surrounding the dorsal aorta and the base of the 

 coeliac and anterior mesenteric arteries. 



In the cervical region the sympathetic system consists of a single 

 longitudinal nerve on each side, which lies in the vertebrarterial 

 canal of the cervical vertebrae, together with the vertebral artery 

 and the vertebral vein. It will not be seen. 



Exercise 24. Draw a diagram of the sympathetic system, so far as 

 observed. 



The Special Sense Organs; the Olfactory Organ. Entirely re- 

 move the skin and muscles from the head ; remove also the eyelids, 

 but do not injure the eyeballs. The nasal capsules consist of a 

 pair of cavities, just in front of the eyes, separated from each other 

 by the median septum nasi. They are in communication with the 

 outside through the nostrils, or external nares, and with the phar- 

 ynx through the internal nares. 



Remove the outer wall of the right capsule completely and 

 observe the interior. Note the slitlike internal nares. In the in- 

 terior are three swellings, the turbinate, which are lateral projec- 

 tions of the septum nasi. Of these the two anterior are prominent, 



