54 AMERICAN FARMER'S HORSE BOOK. 



veloped in the same sheath, and, apparently, one nerve. 

 Each portion, however, continues to be wrapped in its own 

 membrane. They are united, yet distinct ; they constitute 

 one nerve, yet neither their substance nor their office is 

 confounded. 



"All these nerves are organs of sensation and motion 

 alone ; but there are others whose origin seems to be outside 

 of and below the brain. These are the sympathetic, so called 

 from their union and sympathy with all the others, and 

 identified with life itself. They proceed from a small gang- 

 lion, or enlargement, in the upper part of the neck, or from 

 a collection of little ganglia in the abdomen. They go to 

 the heart, and it beats; and to the stomach, and it digests. 

 They form a net-work around each blood-vessel, and the 

 current flows on; they surround the very minutest vessels, 

 and the frame is nourished and built up ; they are destitute 

 of sensation, and they are perfectly beyond the control of 

 the will." 



A later English writer * gives the following clear and com- 

 prehensive summary of the divisions of the nervous system : 



" In the horse, as in all the vertebrata, [those animals sup- 

 plied with a vertebra, or back-bone,] the nervous system is 

 made up of the following parts : 1. The ganglia, which are 

 intended to subserve what are called the reflex actions of 

 the organs of locomotion, etc., and which occupy the whole 

 length of the spinal cord, one on each side. 2. The respiratory 

 ganglia, situated higher up, toward the brain, constituting the 

 part called medulla oblongata, (see p, in cut,) and placed in su- 

 perintendence over the functions of respiration, mastication, 

 and deglutition. 3. A series of ganglia, controlling the organs 

 of special sense, [the sense of sight, of hearing, of taste, etc.,] 

 situated at the base of the brain. 4. The cerebellum, which 

 seems especially intended to combine and balance the several 

 muscular actions of the body. 5. The cerebrum, which is 

 the seat of intelligence and will. 6. The sympathetic sys- 



* J. H. Walsh (Stonehenge). 



