18 



(27.) Connecfion of the hair with the skin — Yolk.-' 

 A hair iinplaated in the skin may be compared to a 

 plant growing in a flower-pot which has been sunk in 

 the earth, as the root of the hair does not rise directly 

 from the true skin, but from a little cup extending from 

 it to the cuticle, and receiving nourishment from sur- 

 rounding vessels. After coming to the surface of 

 these tunics it has, in the sheep, yet another, and, in 

 some respects, remarkable covering to pierce, one 

 which has occupied the attention of the most distin- 

 guished chemists, and given rise to a good deal of dis- 

 putation on the subject of salving — we allude to the 

 Yolk, It is supposed by many to be the inspissated 

 secretion of the sebaceous follicles, and receives its 

 name from its adhesiveness and colour. It is most 

 plentiful on fine-woolled sheep, those of the south pos- 

 sessing more than those of the north of our island, 

 while merinos possess most of all ; so that there is ap- 

 parently some connection between a fine fleece, and a 

 good supply of this matter. According to the analysis 

 of M. Vauquelin, it consists principally of a soapy mat- 

 ter, with a basis of potash ; a small quantity of carbo- 

 nate of potash ; a minute quantity of acetate of potash ; 

 lime in an unknown state of combination ; and an atom 

 of muriate of potash. It owes its odour to a small 

 quantity of animal oil, and is in every respect a true 

 soap, which would permit the sheep to be comjiletely 

 washed in a stream, but for the existence in the fleece 

 of an uncombined fatty matter, which remains attached 

 to the wool, and renders it rather glutinous. 



Many have tried to account for the uses of the Yolk, 

 but nothing like satisfactory conclusions have been 



