30 PROPERTIES OF WOOL, 



YOLK. 



This peculiar substance is so called abroad, from its ad- 

 hesiveness and color ; but with us it is termed gum, an ap- 

 pellation derived from its glutinous properties, quite as 

 appropriate. It is apparent in the fleeces of fine-wool 

 sheep, especially the Merino, at all seasons of the year, but 

 very much so in the winter and spring ; and although ditfused 

 through the whole fleece, yet such is its profusion in the 

 Merino, that it is observable in detached concrete particles^ 

 resembling ear wax. According to the chemical analysis 

 of Vauquelin, it consists principally of a soapy matter, with 

 a basis of potash ; a small quantity of carbonate of potash; 

 a small quantity of acetate of potash ; lirne in an unknown 

 state of combination ; and an atom o{ muriate of potash. Its 

 peculiar odor, well known to those familiar with the fleeces 

 of Saxon and Merino, is derived from the infusion of a small 

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

 which would permit of the fleece being thoroughly cleansed 

 by the ordinary mode of washing, were it not for the exist- 

 ence of this uncombined fatty or oily matter, which remains 

 attached to the wool, and rendering it glutinous, until sub- 

 jected to the process of scouring by the manufacturer. 



There are some, from ignorance, who imagine the yolk or 

 gum to be, if not absolutely a detriment to wool, at least a use- 

 less concomitant. This, however, is a decided mistake. It is 

 a peculiar secretion from the glands of the skin, acting as 

 one of the agents in promoting the growth of the wool, and 

 by its adhesiveness, matting it, and thereby forming a de- 

 fence from the inclemency of the weather. From accurate 

 observation, it has been ascertained, that a deficiency of 

 yolk will cause the fibre to be dry, harsh and weak, and the 

 whole fleece becomes thin and hairy ; on the contrary, when 

 there is a natural supply, the wool is soft, plentiful and 

 strong. The quantity is depending on equability of tem- 

 perature, the health of the sheep, and the proportion of 

 nutritive food it receives. 



Although it is found in greater or less quantities in the 

 fleeces of almost every variety of sheep, such is its excess 

 in the Merino breed, that it causes dirt to collect on the sur- 

 face to such a degree as to form an indurated crust, with a 

 hue resembling the thunder cloud. This excess, although, 

 as already remarked, no way injurious to the fibre, yet in 



