NERVOUS STRUCTURE. 



699 



and before unaccountable state of the surface known as 

 goose-shin. 



Nerves. — The nervous system consists of 

 brain, spinal marrow, and nerves. There 

 are two sets of nerves in the body ; in the 

 one set the nerves are white, firm, shining, 

 more or less rounded, with transverse mark- 

 ings ; in the other, they are softer, not so 

 consistent, of a reddish grey colour, and 

 generally flat. 



Under the microscope, nerves are seen to 

 be composed of minute fibres or tubules, full 

 of nervous matter, arranged in bundles. Fig. 330.-^ std- 



j J.1T. • L ^ • £i.^ ^ late nerve corpus- 



ana connected by an intervening nbro-cei- cie, vntn tubular 



lular tissue, through which capillaries ramify, processes issuing 



. , ' '=> -^ it/ out^ which at a 



A layer 01 the same, or 01 a more delicate, 

 transparent, structureless tissue surrounds 

 the whole nerve, forming a sheath. The 

 slight pressure of the thin glass, when 

 placed on the nerve-fibre, causes nearly the 

 whole of the contents to flow out in the 

 form of a granular material ; it therefore 

 becomes necessary to exercise considerable 

 care in breaking up structures to view these 

 tubules, which should be immersed in a 

 very weak solution of spirit and water. 



On Microscopical Examinatio7i of Nerves It would 



scarcely be necessary to insist on the great importance of 

 removing and examining the 

 nervous centres as soon as 

 possible after death, were it 

 not that the practice is too 

 often neglected. Great cau- 

 tion also should be exercised 

 to avoid injuring the j^arts, so 

 that when hardened, perfect iTfrff:':":":;::,^-^^^^ 



or e?zfl>e sections of them may p.-g 331.-rcrminaffon of nerve-loor^ 



be obtained for examination invmscies. 



under the microscope. After they have been carefully 

 examined externally, by the assistance of a lens, if neces- 

 saijj incisions should be made, not at random, but in a 



IS filled with a 

 Ci>rpusele con- 

 taining black 

 jiigment, above 

 this are corpus- 

 cles with nuclei 

 and their nu- 

 cleoli ; at b is a 

 corpuscle en- 

 closing within 

 its sheath gra- 

 nular matter : 

 this is taken 

 trom the root of 

 a spinal nerve. 



