AND PHYSIOLOGY. 



citing motion. Those from the posterior columns spread 

 through the surface of the body, giving sensation to the skin. 

 The mode, however, in which they terminate is not always the 

 same. As far as at present is known, they seldom terminate 

 in a free or single extremity, but in loops, returning into 

 themselves, or joining with other fibers. And it is an an- 

 atomical fact that the nerve tubes do not anastomose one 

 with the other, as is the case among the blood-vessels ; but 

 each tube discharges its own duty, and not that of another 

 under any circumstances. In the skin of the hand and 

 foot they terminate in minute oval bodies from the r f ^th to 

 the T }oth of an inch in length, and from one twenty-sixth to 

 one twentieth of an inch in breadth, called Pacinian Cor- 

 puscles (from Pacini, their discoverer), and are attached to 

 the branches and extremities of the nerves very much in the 

 same manner as some kinds of fruit are attached to their 

 boughs. (Fig. 326.) Of these, there are about six hundred 

 in the hand and a somewhat smaller number in the foot. They 

 are composed of connective or areolar tissue in from twenty 

 to sixty bands, with interspaces containing a serous fluid, and 

 are attached to their nervous twig by a rounded peduncle. 

 The function of these bodies is entirely unknown. 



603. Sympathetic System — Its Size — Connection 

 with Spinal Nerves — Destination of its Branches. — 



Besides the cerebro- spinal center, there is another organi- 

 zation of nervous tissue which is called the Sympathetic 

 Nerve, or Ganglionic System, and is to be regarded as an 

 appendage of the spinal nerves. It is of very limited size, 

 consisting of mere reddish threads of nervous matter and oval 

 bodies called ganglia, never so large as peas. These ganglia 

 and nerves extend along each side of the spinal column from 



State the manner in which they terminate. Oive a description of the Pacinian cot" 

 puscles. 603. What is said of the structure of the sympathetic system ? 



