THE INTEGUMENT, OR SKIN. 45 



small glands, which produce an oily substance, called se- 

 baceous matter. These glands are little rounded sacs, 

 usually connected with the hair-bulbs; and upon these 

 bulbs, they empty their product of oil, which acts as a, 

 natural and adequate dressing for the hair (4, Fig. 13). A 

 portion of the sebaceous matter passes out upon the sur- 

 face, and prevents the cuticle from becoming dry and hard. 

 The glands situated upon the face and forehead, open 

 directly upon the skin. In these, the sebaceous matter is 

 liable to collect, and become too hard to flow off naturally. 



13. These glands on the face and forehead frequently 

 appear, on the faces of the young, as small black points, 

 which are incorrectly called "worms." It is true, that oc- 

 casionally living animalcules are found in this thickened 

 sebaceous matter, but they can only be detected by the aid 

 of the microscope. This sebaceous matter acts not only to 

 keep the skin flexible, and furnish for the hair an oily 

 dressing, but it especially serves to protect the skin and 

 hair, from the acridity arising from the perspiration. 



14. The Perspiratory Glands. The chief product 

 of the skin's action is the perspiration. For the forma- 

 tion of this, there are furnished countless numbers of 

 little sweat-glands in the true skin. They consist of fine 

 tubes, with globe-like coils at their deeper extremity. Their 

 mouths or openings may be seen with an ordinary magnifying 

 glass, upon the fine ridges which mark the fingers. These 

 tubes, if uncoiled, measure about one-tenth of an inch in 

 length. In diameter, they are about one three-hundredth 

 of an inch, and upon certain parts of the body there are not 

 far from three thousand of these glands to the square inch. 

 Their whole number in the body is, therefore, very great; 

 and, in fact, it is computed if they were all united, end to end. 

 their combined measurement would exceed three miles. 



13. Black pointy called worms? Animalcules? Service performed by seba- 

 ceous matter? 



14. Perspiration? Sweat stands? Of what do they consist? Dimension of 

 the tubes? 



