25-1 



THE CAT. 



[chap. IX. 



22'93 ; pliospliatc of iron, 1*23 ; pliosphate of lime, 1*62 ; phosphate 

 of magnesia, 3 '4 ; chloride of sodium, 4*74 ; sulphate of potash, 

 1*G4 ; free phosphoric acid, 9*15 ; and silicic acid, 0'41. 



The STRUCTURAL ELEMENTS of ncrvous tissuo are mainly of two 

 kinds : (1) fibres, and (2) nei've-cclh or corjyuHclcs. The former of 

 these elements makes uj) the bulk of the peripheral part of the 

 nervous system, while the corpuscles abound in its axial portion and 

 in its scattered ganglia. 



The NERVE FIBRES are again divisible into two kinds : (1) the 

 Kliitc or tubular nerve fibres, and (2) the gre// or^X(f/c fibres. 



The n-hife fibres, which form the bulk of all the nerves except 

 those of the sympathetic system, arc nearly cylindrical filaments 



C 



^ii. 



2 3 2 



I-Ml'. 1:;1.— Wihtk Nerve Fibues. 



A. Wliitc nr iiicilullattMl iicnc-libivs, slinwiiij,' 



tliiiir sinuous dutliiii! and dcjublo (•oiit(nir.s. 

 I!. Diagram showing tlie parts of a nRMlnllatcil 

 filni', viz. : 



1 — 1. rrimitlrc slicnth. 



'J— 'J. Tin; wliite substance, or 'imdidlnry 



slir((tli. 

 ". Tlie axi.s-libre, or axis-rylindcr — sonie- 

 tinn's cidhMl tlic iiriniitivi' ban<l. 

 C. Diagram intt-ndi'd to n']irus(;nt ai)jpearant('S 



occasionally seen in tlie tubular fiTires, viz. 

 1—1. Menibiane of till' tube, .seen at part 



where the white .substance has separatetl 



fi'oni it. 

 2. A ])art where the white .substance is 



interruiitcd. 

 :?. Axis ]irii.jectiiig bryond the broken end 



of the tube. 

 4. I'arts of the contents of the tube which 



have esca)ied. 



which, during life, seem composed of a clear, oily, semi-fluid sub- 

 stance, but after death, appear as composed of a delicate structureless 

 outer membrane — the primitive sheath (like the sarcolemma of muscle 

 fibre), provided witli large nuclei, and coutnining fatty fluid termed 

 the meduUarji shcutJi or n-Jiite substance of Scliu-aini, through wliich 

 runs a thin central thread of albuminoid matter called the aa-is cf/liiidcr. 

 The largest of these white nerve-fibres has a diameter of about 

 the TaVo- of an inch, bufe some of only TTo-iy-o-- They may be larger 



