308 



HITCHCOCK'S 



ANATOMY 



it will not retain all dust which chances to fall upon it. At 

 the flexions of the joints, and all those places where two sur- 

 faces of the skin are frequently brought in contact, this oily 

 secretion is abundantly poured out, in order that there may 

 be as little friction as possible between the opposing surfaces. 

 Upon the edges of the eyelids is situated a row of glands which 

 pour out their secretion in such a manner as to retain the tears 

 — the lubricating fluid of the eye — when produced in their 

 ordinary quantity ; but when in excess, as in weeping, they 

 run over their boundaries, and flow down the cheek. The use 

 of these glands may be well appreciated in some diseases of 

 the eye, where the tears constantly run down upon the cheek, 

 producing irritating sores. 



In the passages of the ears we find the same glands, al- 

 though their secretion is of a somewhat different character. 

 Here it is a clammy, viscid substance, of a yellowish color, 

 and from its appearance it is called the wax of the ear. Its 

 service is to prevent dust and foreign substances generally 

 from gaining access to the internal ear, where they would 

 injure the sense of hearing. 



HYGIENIC INFERENCES. 



540. — 1. Great Value of this Membrane in the Ani- 

 mal Economy. — From the complicated structure of the skin, 

 we see that this membrane is of great service in the animal 

 economy. It stands next in importance to the lungs as an 

 excretory organ, and if its functions are interrupted the whole 

 system very soon feels the disturbance. 



541. — 2. Its Health Requires Cleanliness. — The skin 

 must be kept clean to secure the proper functions of the per- 

 spiratory glands. This not only implies the necessity of fre- 



II ow does it affect the skin at the joints ? Of what service is it to the eye ? Of what 

 to the ear? 540. State the relative value of the skin in the animal economy. 541. Why 

 is cleanliness essential for the health of the skin '? 



