SYMPATHETIC NERVE AND OFFSETS. 



341 



right side of the head and neck pour their contents. In addition, the 

 lymphatics of the right side of the chest, right lung and right half of the 

 heart, and some from the right lobe of the liver, after passing through their 

 respective glands, unite into a lew large trunks, which ascend beneath the 

 innominate vein to reach the duct in the neck. 



Structure of the ducts. The wall of the tube resembles that of the 

 bloodvessels in structure (p. 119). 



CORD OF THE SYMPATHETIC NERVE. The thoracic part of the gan- 

 gliated cord of the sympathetic nerve is covered by the pleura, and is placed 

 over the heads of the ribs, and the intercostal vessels. The ganglia on it 

 are usually twelve, one being opposite each dorsal nerve, but this number 

 varies much. The upper ganglion is the largest ; and the last two are 

 rather anterior to the line of the others, being situate on the side of the 

 bodies of the corresponding vertebras. 



Each ganglion furnishes external branches to communicate with the 

 spinal n ;rves, and internal for the supply of the viscera. 



External or connecting branches (fig. 107). Two offsets pass outwards 

 from each ganglion to join a spinal nerve (intercostal). In the branches 



Fig. 107. 



a. Posterior root of a spinal nerve, with a 



ganglion, c. 



b. Anterior root. 



d. Posterior primary branch. 



e. Anterior primary branch of the spinal nerve. 

 /. Knotted cord of the sympathetic. 



g. Ganglia on the cord. 



h. White offset from the spinal to the sympa- 

 thetic nerve. 



i. Gray offset from the sympa hetic to the 

 spinal nerve. 



SCHEME TO ILLUSTRATE THE CONNECTION BETWEEN THE SPINAL AND SYMPATHKTIC NKRVES. 



(Todd and Bowman.) 



of communication both spinal and sympathetic nerve fibrils are combined : 

 but one (h) consists almost entirely of spinal, and the other (/) nearly al- 

 together of sympathetic nerve fibres. 



The internal or visceral branches differ in size and distribution, accord- 

 ing as they are derived from the upper or lower six ganglia. 



The offsets of the upper six are very small, and are distributed to the 

 aorta, and the vertebra? with the ligaments. Mr. Swan describes a plexus 

 in front of the spine, from the union of the branches of opposite sides. 



