STRUCTURE OF WOOL. 



143 



derma. It is in the derma that the hair is rooted, and from it 

 that it is nourished. The hair, (or wool), consists of two portions, 

 the shaft, or that which pierces through the epidermis and forms 

 the outer coat or fleece, and the bulb or root which is imbedded in 

 the derma. The bulb of the hair is rooted in a gland called the 

 hair follicle, and from this it derives the cells which form the outer 

 surface of the hair. These cells are converted into flat scales, in- 

 closing the interior fibrous structure of the hair, and as they are 

 successively produced, they overlap like shingles on a roof, or the 

 scales of a pine cone, forming the imbricated coat of the hair to 

 be hereafter described at length. Rising into the hair bulb is the 

 hair germ, which furnishes the hair with nutrition, and the ele- 

 ments of its growth. On each side of the hair follicle is a gland 

 which secretes a viscid fluid. These glands, known as the sebace- 

 ous glands, open by small canals into the sheath of the hair. Other 



Fig. 47. SECTION OP SKIN HIGHLY MAGNIFIED, SHOWING THE GROWTH 

 OF THE HAIB. 



sebaceous glands open independently upon the surface of the epi- 

 dermis. They secrete a fluid which serves to lubricate the skin, 

 and in the sheep supplies the oil and yolk that fill that pur- 

 pose for the fleece and prevent any injury to the wool by con- 

 tinued rubbing, or " cotting," or felting, in consequence of the 

 wearing and friction, while upon the sheep's back. In a healthy 

 skin this secretion with those of other glands, (called the sudori- 



