536 



NERVOUS SYSTEM. (NERVOUS MATTER.) 



regards their physical properties; and, as ap- 

 pears not unreasonable to conclude, capable 

 of manifesting a distinct series of vital forces. 



If great strength and power of resistance be 

 requisite, a particular form of animal matter 

 (gelatine) is united with an earthy material to 

 constitute bone ; for the developement of 

 strength, combined with elasticity or flexibility, 

 this same kind of animal matter, or a modifi- 

 cation of it, is again employed, containing 

 none or a very slight proportion of earthy ma- 

 terial, and forming the various kinds of cartilage 

 and ligament; but for the play of the active 

 powers of life for the developement of living 

 movements whether in the performance of 

 the nutritive functions, in growth and repro- 

 duction, or in the display of muscular force 

 and activity, two substances, the most complex 

 in chemical constitution of any in the body, 

 and possessing the greatest atomic weight, are 

 made use of to form the structures, on which 

 these remarkable phenomena depend, namely, 

 muscle and nerve. These structures are com- 

 posed respectively of fibrine and albumen ; 

 they are organized in analogous forms, and by 

 their mutual reactions they exhibit the mar- 

 vellous effects which animal power is capable 

 of producing. 



GENERAL OBSERVATIONS ON THE DISPOSITION 

 AND COMPOSITION OF THE NERVOUS MAT- 

 TEH, THE NATURE OF NERVOUS ACTIONS, 

 AND THE SUBDIVISIONS OF THE NERVOUS 

 SYSTEM. 



The nervous matter presents the singular 

 peculiarity that it alone, of all the varied forms 

 of animal texture, is directly influenced by the 

 mental acts of animals. It is that part of the 

 organism through the immediate agency of 

 which mind operates upon body and body 

 upon mind. Through this connexion with the 

 psychical principle of the animal, sensation is 

 produced, and volition is enabled to exercise 

 its influence on muscular organs. And in the 

 whole range of the mysterious phenomena, which 

 the student of nature meets with, there is no- 

 thing so inscrutable as the fact that the work- 

 ings of the mind can disturb and impair the 

 organization of the nervous matter ; or, on the 

 other hand, that the disorganization of the ner- 

 vous matter is capable of deranging mental 

 manifestations. 



The existence of this remarkable and pe- 

 culiar kind of organic matter is limited to the 

 animal kingdom, and is therefore one of the 

 characteristic features of animals as distin- 

 guished from plants. It is obviously the pre- 

 sence of a psychical agent controlling and di- 

 recting certain bodily acts of animals, which 

 has called into existence the particular appa- 

 ratus which the nervous matter is employed to 

 form. 



In the largest proportion of the animal king- 

 dom, the nervous matter is so disposed or 

 arranged as to form a system complete in 

 itself, and distinct from, although connected 

 with, the other textures and organs. This is 

 called the NERVOUS SYSTEM the deve- 

 lopement of which has always a direct relation 



to the bodily organization and psychical endow- 

 ments of the animal. 



The nervous matter is accumulated into 

 masses, forming what are denominated CEN- 

 TRES of nervous actions ; and it is also deve- 

 loped in the form of fibres, filaments, or mi- 

 nute threads, which, when bound together, 

 constitute the NERVES. The latter are in- 

 tcrnuncial in their office; they establish a 

 communication between the nervous cen- 

 tres and the various parts of the body, and 

 vice versa ; they conduct the impulses ot the 

 centres to the periphery, and carry the impres- 

 sions made upon the peripheral nervous rami- 

 fications to the centres. Nor are the nerves 

 mere passive instruments in the performance of 

 their functions; but produce their proper effects 

 through their susceptibility to undergo molecu- 

 lar change under the influence of appropriate 

 stimuli. 



The centres are the great sources of ner- 

 vous power; they are the laboratories in which 

 the nervous force is generated. The mind 

 appears to be more immediately connected 

 with one of them, which, pre-eminent on that 

 account, exerts a certain control or influence 

 over its fellows. 



In the centres there are two kinds of ner- 

 vous matter, distinguished by certain anato- 

 mical characters and by certain physiological 

 properties and uses. The one is globular or 

 vesicular in structure, grey in colour dynamic 

 as regards office. The other is h'brous, its fibres 

 being tubes containing nervous matter; it is 

 white in colour, and is devoted to act as a 

 conductor of impulses to and from the grey 

 matter. The white matter is that of which the 

 nerves are composed, and the two kinds of 

 matter do not occur together any where but in 

 the nervous centres ; in fact, their co-existence 

 in any part of the nervous system is sufficient 

 to constitute that part a centre of nervous action. 



In the lowest creatures the existence of ner- 

 vous matter is as yet problematical. It is 

 supposed by some physiologists that it is dif- 

 fused in a molecular form throughout the body 

 of the animal, and the muscular tissue being 

 likewise disposed in a similar way, the one 

 may act upon the other at every point. Were 

 this supposition true, it might be further con- 

 jectured that, under such circumstances, only 

 one kind of nervous matter, the dynamic, would 

 exist; for as the office of the white nervous 

 matter is chiefly to propagate or conduct to 

 distant parts the changes which originate in 

 the grey matter, the former would not be re- 

 quired in animals, in which the elements of 

 the grey matter are in contact with those of the 

 other textures at every part of the body. 



The form in which nervous matter first de- 

 velopes itself as a distinct tissue is in that of 

 threads or cords, into the composition of which 

 areolar tissue and bloodvessels generally enter. 

 The class of animals in which this arrangement 

 prevails has been designated by Mr. Owen 

 Nematoncura ; and, in many of these at least, 

 the existence and the disposition of grey matter 

 have yet to be ascertained. 



The nervous matter of both kinds is a sub- 



