330 



SECRETION. 



too rapid evaporation. When the sebaceous glands of the scalp 

 are inactive or atrophied, the hairs become dry and brittle, are 

 easily split or broken off, and finally cease growing altogether. 

 The cerurainous matter of the ear is intended without doubt partly 

 to obstruct the cavity of the meatus, and by its glutinous consist- 

 ency and strong odor to prevent small insects from accidentally 

 introducing themselves into the meatus. The secretion of the 

 Meibomian glands, by being smeared on the edges of the eyelids, 

 prevents the tears from running over upon the cheeks, and confines 

 them within the cavity of the lachrymal canals. 



3. PERSPIRATION. The perspiratory glands of the skin are scat- 

 tered everywhere throughout the integument, being most abundant 

 on the anterior portions of the body. They consist each of a slender 

 tube, about 7 <y of an inch in diameter, lined with glandular epi- 

 thelium, which penetrates nearly through the entire thickness of 

 the skin, and terminates below in a globular coil, very similar in 



appearance to that of the cerumi- 

 Fig. 104. nous glands of the ear. (Fig. 104.) 



Yt A network of capillary vessels 



envelops the tubular coil and sup- 

 plies the gland with the materials 

 necessary to its secretion. 



These glands are very abundant 

 in some parts. On the posterior 

 portion of the trunk, the cheeks, 

 and the skin of the thigh and leg 

 there are, according to Krause, 1 

 about 500 to the square inch ; on 

 the anterior part of the trunk, the 

 forehead, the neck, the forearm, 

 and the back of the hand and foot 

 1000 to the square inch ; and on 

 the sole of the foot and the palm 



of the hand about 2700 in the same space. According to the same 

 observer, the whole number of perspiratory glands is not less than 

 2,300,000, and the length of each tubular coil, when unravelled, 

 about YS of an inch. The entire length of the glandular tubing 

 must therefore be not less than 153,000 inches, or about two miles 

 and a half. 



A PERSPIRATORY G LAND, with its ves- 

 sels ; magnified 35 times. (After Todd and Bow- 

 man.) a. Glandular coil: b. Plexus of vessels. 



Kolliker, Handbuch der Gewebelehre, Leipzig, 1852. p. 147. 



