376 FUNCTIONS OF THE NERVOUS SYSTEM. 



provement of the knowledge and happiness possessed by our race, operat- 

 ing alike in the common affairs of life, by suggesting those pictures of the 

 future which are ever before our eyes, and are our animating springs of action, 

 with their visions of enjoyment never perhaps to be fully realized, and their 

 prospects of anticipated evil that often prove to be an exaggeration of the 

 reality, prompting the investigations of Science, that are gradually unfolding 

 the sublime plan on which the Universe is governed, and leading to a con- 

 tinual aspiration after those highest forms of Moral and Intellectual beauty, 

 which are inseparably connected with purity and love. 



8. General Recapitulation and Pathological Applications. 



496. A general Summary of the views here propounded, in regard to the 

 Functions of the Cerebro-Spinal division of the Nervous system, may proba- 

 bly be useful in assisting the Student to gain clear ideas regarding them. 

 The fibres of the nervous trunks may be divided, according to the direction 

 of their influence, into two classes, the afferent or centripetal, and the effe- 

 rent or centrifugal. The afferent may be said to commence at the periphery, 

 especially on the skin, mucous surfaces, &c., and to terminate in the vesicu- 

 lar matter of the nervous centres ; whilst the efferent originate in that vesicu- 

 lar matter, and terminate in the muscles.* Every fibre runs a distinct course 

 from its origin to its termination ; and it is not improbable that there are 

 several distinct endowments in the different fibres composing each trunk. 

 There is no evidence that the fibrous structure serves any different purpose 

 than that of a mere conductor; and there seems good reason to believe that 

 all the active operations, of which the nervous system is the instrument, ori- 

 ginate in the vesicular matter. A mass of vesicular matter, connected with 

 nervous trunks, forms a ganglion. In the Invertebrata, the ganglia are fre- 

 quently numerous, and are scattered through the system, without much con- 

 nection with each other; each having an independent action, although its 

 function may be but a repetition of that of others. In Vertebrated animals, 

 on the other hand, they are united into one mass ; partly, it would seem, for 

 the sake of the protection afforded them by the bony skeleton ; and partly, 

 in order that more complete consentaneousness of action may be attained. 

 Still, certain divisions may be traced in the central masses of the Cerebro- 

 Spinal system ; both by the determination of their respective functions, as 

 indicated by observation and experiment ; and by the study of the distribution 

 of the nerves proceeding from them. In this manner we arrive at the know- 

 ledge of several distinct ganglionic centres, of which the following may be 

 considered as a general account. 



i. The True Spinal Cord, consisting of a nucleus of vesicular matter, re- 

 ceiving afferent fibres, and giving origin to efferent ; by these it is connected 

 with all parts of the body, but especially with the surface and muscles of the 

 extremities. The actions of this centre maybe performed without conscious- 

 ness on the part of the individual; and they consist in the reflexion of a motor 

 impulse along an efferent nerve, on the reception of a stimulus conveyed by an 

 afferent or excitor nerve. These reflex movements can be best excited, when 

 the muscles are removed from the control of the Will, which otherwise gene- 

 rally antagonizes them. Some of them are connected with the maintenance 



* The terms originate and terminate cannot be used with strict correctness; since, as for- 

 merly explained ( 2-18), many libres seen} to have no actual termination, either in the mus- 

 cles or in ve.-ienl:ir mutter: but they cease to rim in then previous direction, after forming 

 their terminal loops; and tlieir course as afferent or efferent fibres may consequently be said 

 to begin or to end at these points. 



