214 ELEMENTS OF MAMMALIAN ANATOMY. 



Other nerves given off from the sacral plexus are the 

 glutei and pudic nerves supplying the buttock muscles and 

 external genital organs. 



THE SYMPATHETIC NERVOUS SYSTEM. 



The sympathetic nervous system is composed chiefly of a 

 pair of nerve-cords extending from the base of the skull to 

 the root of the tail, a number of ganglia and branches 

 supplying the thoracic and abdominal viscera, and numerous 

 minute fibers supplying the muscular walls of the blood- 

 vessels in all parts of the body. The sympathetic system 

 supplies all non-striped or involuntary muscles in any part 

 of the body. The two branches connecting each spinal 

 nerve with a sympathetic nerve cord are called rami com- 

 municantes. 



In order to demonstrate this system successfully, one 

 should use a lean injected specimen. After the cat has been 

 securely nailed on its back to the tray, the entire ventral half 

 of the. thoracic and abdominal walls should be removed. 

 By pushing the heart and lungs to the left side a white cord 

 about one millimeter in diameter may be seen lying near the 

 median dorsal line (Fig. 107) . The left cord may be found 

 in a similar manner and both followed craniad and caudad, 

 noting their numerous branches in accordance with the fol- 

 lowing description. 



The sympathetic nerve-cord begins in the superior cer- 

 vical ganglion lying near the angle of the mandible, beneath 

 the submaxillary and lymphatic glands. This ganglion is 

 about the shape of a grain of wheat, but not more than half 

 so large, and is adjacent to the small vagus ganglion on the 

 dorsal side of the carotid artery. The ganglia are masses 

 of large nerve cells and occur at regular intervals on the 

 sympathetic cords in the body cavity, and are present also on 

 some of the branches of the cords (Fig. 108). On the 



