I IO 



HAIRS. 



[sect. 60. 



The diameter of the medulla is, in general, to that of the hair 

 itself as i to 3 — 5 ; it is relatively and absolutely thickest in short 

 thick hairs, thinnest in woolly hairs and those of the head. In a 

 cross section it has a round or flattened figure ; and the cells which 

 compose it are arranged in 1 — 5, or even more longitudinal rows. 



According to Reissner and JReichert, the medulla contains in its 

 interior a fine fibre, which is a prolongation of the hair-papilla ; a 

 statement which I have not hitherto been able to confirm. 



§ 60. The cuticle of the hair is a very thin transparent mem- 

 brane, which forms a complete covering for the hair, and is very 

 firmly united with the cortical or fibrous substance. When viewed 

 in its normal position and in an unaltered hair, its almost sole 

 indications are numerous, dark, reticulated, irregular, and even 

 jagged lines, which are distant 0002'" to 0"Oo6"' from each other, 

 and extend round the hair, and small projections giving a ser- 

 Fig. 49. rate outline to its appa- 



rent border (fig. 49, A.) . 

 If a hair be treated with 

 alkalies, the cuticle sepa- 



rates in larger or smaller 

 shreds from the fibrous 

 substance,and even breaks 

 up into its elements. 

 These are quite flat, non- 

 nucleated plates, gene- 

 rally transparent and 

 pale at the borders, and 

 of a quadrangular or rectangular outline, which do not swell up 

 into vesicles by means of re-agents. They are arranged like tiles 

 on a roof, the lower cells overlapping the upper ones, and form a 

 simple membrane, which entirely envelopes the cortex or fibrous 

 part of the hair. In sulphuric acid, also, the structure of the 

 cuticle can be easily perceived ; the hair becomes ragged at the 

 borders, from the projection of the plates, and then the cuticle can 

 be easily scraped or rubbed off; but it is reduced to its constituent 

 elements, and it is not easily obtained in larger patches. 



The cuticle consists of a single layer of plates or scales, which 

 on the shaft is o , oo2'" to o , oo3'", on the root o , oo25' // to o"oo35'" 

 thick ; the plates measure, in the transverse direction, o"024'" to 

 o'lS'" ; in the longitudinal, o'Oi6'" to 0*02'"; and are scarcely 

 thicker than o"0005'". At the hair-bulb these plates pass rather 



A. Surface of the shaft of a white hair, magnified 1G0 times. 

 The curved lines designate the free border of the epidermic 

 plates. B. Epidermic plates from the surface, isolated by caustic 

 soda, and magnified 350 times. Either one or both of their 

 borders are folded, and consequently appear dark. 



