CHAP, ix.] NERVOUS SYSTEM AND ORGANS OF SENSE. 



285 



The sympathetic system may be regarded either as a separate 

 system or as but a series of internally directed branches of the 

 spinal nerves of each side of the body. According to this latter 

 view, each spinal nerve divides into three branches. One of these 

 branches passes upwards as a dorsal nerve ; another follows the 

 body wall the ventral branch of each spinal nerve while the third 

 branch (hitherto called the filament to the sympathetic) passes in- 

 wards in the line of the mesenteries. These last inner branches or 

 filaments are serially connected by horizontal nerves, i.e., by the two 

 longitudinal gangliated cords. 



The sympathetic filaments which ramify around the arteries are 

 termed the mso-motor nerves. 



THE ORGANS OF SPECIAL SENSE 



22. Feelings of different kinds will be more fully considered 

 amongst the functions of the nervous system, but their existence 

 must be recognized in treating of the organs which minister to them, 

 and these have now to be considered. 



The special ORGAN OF TOUCH is the skin, above all the skin of 

 the muzzle, tongue and digits. The nerves of the vibrissao and the 

 touch corpuscles are the agents which induce this sensation. 



The structure of the skin, with its papillae, the touch corpuscles and 

 Pacinian bodies have been already described in the second chapter. 



The nerves at their ultimate terminations in the skin, divide, and 

 may form small terminal plexuses, or enter touch corpuscles or 

 Pacinian bodies (as earlier described), or terminate in end bulbs, 

 which are spheroidal bodies about ^- of an inch in diameter. 

 Each of these consists of a capsule of connective tissue, with nuclei 

 the capsule containing a core of clear, soft, granular matter. 



23. The ORGAN OF TASTE is, in the main, the tongue, especially 

 its back part, but the under surface of the soft palate also seems to 

 participate in the faculty. The tongue with its three kinds of 

 papilla), has been already described. It is supplied with three 

 nerves : (1) the gustatory, (2) the lingual branch of the glosso- 

 pharyngeal, and (3) the hypoglossal. The last is motor, but the first 

 two are sensory. The gustatory nerve goes to the mucous membrane 

 and papillae of the fore-part and sides of the tongue, the lingual 

 branch of the glosso-pharyngeal goes to the mucous membrane at 

 the base and side of the tongue, and especially to the circumvallate 

 papillae. 



The soft palate and also the anterior pillars of the fauces, have 

 short, soft papillae on their mucous membrane, and these parts are 

 supplied with fibres from the superior maxillary and glosso-pharyn- 

 geal nerves. 



The parts, however, which by their contact with foreign bodies 

 are the actual ultimate occasions of the sense of taste are certain 

 minute structures called GUSTATORY CELLS, which are enclosed in 

 other structures called GUSTATORY BULBS. These latter are very small 



