188 THE HUMAN MECHANISM 



of solids in the ducts of the glands is washed out. For this 

 reason a vigorous perspiration followed by a bath is a useful 

 hygienic measure in the care of the skin, although it is not 

 necessary, as is sometimes supposed, in order to secure the 

 efficient elimination of wastes from the blood. 



10. The skin as an organ of absorption. While it is true 

 that water as perspiration may readily find its way out 

 through the skin, such escape is effected chiefly by the 

 sweat glands, which are under the strict control of the nerv- 

 ous system. Apart from this the skin is virtually water- 

 tight; and, oiled as it is by the secretion of the sebaceous 

 glands, it serves both to keep in the water, which forms so 

 important a part of the tissues, and also to keep out water 

 which might otherwise soak into the body, as, for example, 

 during bathing. This waterproof characteristic also makes it 

 next to impossible for us to absorb food materials by way of 

 the skin. A " milk bath" may be at times useful in the care 

 of the skin, because the fat or oil of the milk may supply 

 any deficiency in the sebaceous secretion and so insure 

 lubrication of the epidermis ; but it cannot be regarded as 

 a means of supplying food to the body. 



