HISTOLOGICAL DEMONSTRATIONS. 127 



upon it, cover and examine. In a hair three parts may 

 usually be distinguished : i. The cuticle, consisting of a 

 layer of epidermic scales arranged in an imbricated fashion ; 

 2. The cortex, composed of a substance which often appears 

 almost homogeneous, with a few longitudinal lines and gra- 

 nules scattered through it, but which, on bruising a hair that 

 has been boiled in sulphuric acid, is found to consist of epider- 

 mic scales elongated and resembling fibres ; 3. The pith, 

 consisting of irregular cavities amidst the epidermic fibres. 

 These cavities are often absent. The pigment of the hair 

 is either in the form of masses of granules scattered through 

 the cortex, or is diffused throughout the epidermic matter. 



228. Hair of Sheep. (H.) Mount in dammar. Ob- 

 serve the strongly marked borders of the cuticular cells, 

 readily seen in profile. 



229. Hair of Babbit (H.) Mount in dammar. Ob- 

 serve the single or double row of cavities in the pith, and 

 the relatively small amount of fibrous cortex. 



230. The Hair Follicle. The hair in its follicle is 

 enclosed in envelopes derived from the dermis and epider- 

 mis. From without inwards, the envelopes are 



I. Dermic Coverings. 



1. A layer of white fibrous tissue with its bundles 

 arranged longitudinally. 



2. A fibrous layer of somewhat indeterminate character, 

 the connective tissue corpuscles and the indistinct fibres 

 around them being arranged transversely. 



3. A hyaline layer of doubtful structure, resembling a 

 basement membrane. 



II. Epidermic Coverings. 



4. The outer root sheath, consisting of a mass of cells 

 irregularly disposed, continuous with the rete mucosum of 

 the adjoining skin. 



5 . The inner root sheath, composed of two layers : 



a. Hentts layer (fenestrated layer), made up of a 



