440 



M ItVll 



NKi;\m s >\ >TI:M 



Octane, In*, Emilir, Corilla ( 1858). Another book 

 of singular interest U the melange entitled La 

 Bohfme dalaitli Some of his mutt charming 

 poems are graceful adaptations of French peasant* 

 folk-gongs, the beauty of which he had ears to hear. 

 His iKurrrt compUttt were collected in 5 Toll, in 1&68. 

 See Andrew Lang in t'rotrr't Alayatint, May 1873. 



\iTii, n |Mi\vi>rfiil ami warlike people of the 

 ancient (iallia lielgica, whose territory stretched 

 from the Samlne to ilic ocean, not subdued by 

 Cmar without an olwtinate resistance. 



Xervous Itlxeases. See articles in this 

 work mi Alcoholism, Aphasia, Apoplexy, Appe- 

 titf. liniin, Chorea. Cri'tinisin, Delirium, Delinum 

 'Piemen-, F.pilepsy. Headache, Hydrocephalns, 

 1 1 v pochondriasis, lly-iciia. Insanity, l.oeomotor 

 Ataxia. Meningitis HTelitfa, Neuralgia, Paralysis, 

 Sciatica. Spinal Conl, Sunstroke, Tetanus, &c. 



N'KKVorsNKSS is a term somewhat vaguely used, 

 Inith popularly and by medical men, to express an 

 unduly excitable condition of the nei vons s\stem, 

 manifested by unusually ready manifestation of 

 emotion e.g. starting at slight causes -by morbid 

 sensitiveness by unreasonable apprehension, by 

 trembling of muscles, and in many oilier \va\s. 

 The condition may IK- natural, or produced by ill- 

 health or acute disease. It is more common in 

 children than in adults, and in the female sex than 

 the male. Care should be taken to improve the 

 general health by good nutrition, regulation of 

 the bowels, open air exercise, bathing, change of air 

 and scene, and the ordinary tonic remedies; -limu- 

 lantw and drug's should be avoided save under the 

 special direction of a medical man. 



Nervous System, the mechanism by which 

 an animal acquires a knowledge of the external 

 world, and by means of which the great functions 

 of the absorpt ion of fund, the elimination of waste 



Iiroducts from the Imdy, the respiration, circu- 

 ation, and muscular action, are regulated and 

 emit rolled. In ils simplest form, in some of the 

 lowest animals, it consists merely of nerve-fibres 

 going to and from a small group of nerve-cells ; but 

 from this elementary condition there is an ever- 

 increasing degree of complexity till its highest 

 development is reached in man, which alone is 

 included in the following description. In the 

 articles on Birds, Fishes, Reptiles, Mollusca, &c. 

 will In- found paragraphs on the nervous systems 

 of the various classes of animals. 



The nervous system is composed of a series of 

 organs nerve ceils, nerve-fibres, and nerve end- 

 organs. The nerve-cells are situated for the most 

 part in the brain and spinal cord, but also in 

 other pails of the nervous system. Their function 

 is either to receive, to send out, or to modify as 

 they transmit, nervous impulses. The nerve 111 ires 

 transmit nerve impulses to and from the nerve- 

 cells. For this reason groups of nerve-cells are 

 often conveniently spoken of as nerve centres; 

 tlieir relation to the nerve-libres lieing analogous 

 to that of a telegraph -office to the wires connected 

 with it. The end -organs are the special structures 

 for receiving impressions, such as tin; various 

 organ" of special sense, smell, sight, hearing, tftste, 

 kmeh(M0non, KVB, EAR, TASIK, TUITH), and 

 for transforming outgoing impulse- inio muscular 

 contractions or secretion. Ac. The nerve-fibres 

 thus connect either an end-organ with a nerve 

 centre, or two nerve centres with each other. 

 These three sets of organs, nerve centres, fibres, 

 and end-organs, are grouped into two great 

 systems the ./('</<-//// dig. 1) and the XI/IH- 

 jiiitlirtu- ( fig. 10) system. The former is composed 

 of the brain, spinal cord, and the cranial and spinal 

 nerves resix>ctively connected with them. The 

 ympathetic system is formed by a double chain 



ill -mall swellings, called ganglia, on either 

 of the front of the spinal column, and connected 

 with each other, with the spinal nerves, and the 

 internal organs by fine nerve-fibres (figs. 7 and 10). 



. 1- 



o, cerebrum ; b, orrrU'llutn ; <. medulla nblongata ; d, spinal 

 cord, from which ihe spinal nerve* anw ; t, bracliUl plexus ; 

 /, sciatic nerve. 



The nerves are whitish cords varying greatly in 

 size. They are composed of nerve-libres which are 

 hound together by fibrous tissue. This forms a 

 sheath on the outaide, (the /n-rnieiirium ), and sends 

 processes inwards lietwecn the individual nerve- 

 libres (fig. 4 shows a traiis\ci-e section of part of a 

 nerve, with the bunding of connective tissue passing 

 inward). In the spinal cord and brain the nerve- 

 fibres are held together by a special kind of con 

 nective tissue, called nenroglia. 



Structure of Nerm-fibres. A fibre from a spinal 

 nerve has the following structure. In the centre 

 is a very fine lilire or thread called the ><i ,n . iilintier. 

 This runs without any interruption along the whole 

 lenu'lli of the nerve. It can be traced into a nerve 

 eel fat one extremity, anil into an end organ at tin- 

 oilier: and there is reason to lielieve that it is 

 really an outgrowth from a nerve cell. It is the 

 es-ential constituent of a nerve, that namely along 

 which the nervous impulse travels. The axis 

 cylinder is in its turn composed of still liner 

 fibrillie, which may break up into liner nerve 

 fibres. Kxcept at its origin ami termination, the 

 axis cylinder i- covered by a tubular membrane 

 called 'tin- iiii'/nlt'irtf xlinilli. or the white sub- 

 stance of Schwaiin, a whitish substance of a 

 peculiar fatty nature. This is Interrupted at inter- 

 vals of alMiut ,'jth of an inch by const rid inns which 

 ( lig. 2) pass completely through its thickness. When 

 a nerve is stained with nitrate of silver, a black 

 colour is formed at the intersections, and for a 

 short distance along the axis cylinder (see fig. 3, 

 where two are represented ). These interruptions 



