214 ELEMENTS OF MAMMALIAN ANATOMY. 
Other nerves given off from the sacral plexus are the 
glutci 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 
