556 DBS. GEOKGE AND FEAKCES E. HOGGA]!? ON 



largest of these hairs in the Horse. They arrive on the feelers about 

 the level of the lower extremity, and pass np alongside the follicle 

 in bundles which become more numerous as they pass upwards. 

 These bundles may either lie imbedded in the gelatinous tissue 

 external (as regards the hair) to the basement-membrane, as 

 at d, fig. 13, Plate XIV. ; or they may pass through the 

 cavity of the blood-sinus, as at (7*, in which case, whether it be 

 a single nerve or a large number of them in a bundle, they are 

 always surrounded by a thick coating of gelatine. In the ordi- 

 nary hairs the nerves may be only one or two in number, which 

 generally approach the hair at a much higher level than in the 

 case of the feelers, and, it may be, from opposite sides of the hair. 

 In the immediate neighbourhood of the hair each fibre may divide, 

 and even subdivide, into two or more branches or independent 

 fibres, each of which has its own special set of terminations, as 

 seen at a, fig. 7, Plate XIII. 



In these nerves the medulla or myeline is an insulating sub- 

 stance or sheath of the nature of fat, which is placed upon the 

 axis-cylinder or true conducting nerve in segments of equal 

 length, which bear the same relation to the axis-cylinder that 

 long bugle beads bear to the thread upon which they are strung, 

 each bugle-bead-like element being a complex cell resembling 

 the fat-cell in character, and possessing protoplasmic walls, a 

 centrally placed nucleus, and cell-contents of an oily cha- 

 racter, which form the insulating substance. As seen in fig. 7, 

 Plate XIII., when a nerve breaks up into two branches, the divi- 

 sion always takes place at the end of one of the insulating seg- 

 ments, where the two new segments on the now bifurcated nerve 

 or axis-cylinder are applied. Sometimes only one of the bifur- 

 cations is provided with a myeline- sheath, if near its termina- 

 tion, as at i, fig. 7, the other bifurcation breaking up into several 

 non-medullated nerve-fibrils, as shown there. Or a nerve may 

 lose its insulating sheath some distance before it breaks up into 

 its ultimate termination, as seen at Ic, where the axis -cylinder 

 may also be distinctly traced as it lies within its last insulating 

 segment *. 



* For more minute information respecting the medullated nerve-fibrea, see 

 our articles "Sur les changements subis par le systeme nerveux dans la lepre" 

 (Archives de Physiologic, 1882), and " De la degeneration et de la regeneration 

 du cylindre-axe " (Journal de I'Anatomie, 1882), copies of which are in the 

 Society's library. 



