346 HAND-BOOK OF PHYSIOLOGY. 



effects. Vegetable matters, also, if soluble, or already in solution, give 

 rise to their peculiar effects, as cathartics, narcotics, and the like, when 

 rubbed into the skin. The effect of rubbing is probably to convey the 

 particles of the matter into the orifices of the glands, whence they are 

 more readily absorbed than they would be through the epidermis. When 

 simply left in contact with the skin, substances, unless in a fluid state, 

 are seldom absorbed. 



It has long been a contested question whether the skin covered with 

 the epidermis has the power of absorbing water; and it is a point the 

 more difficult to determine because the skin loses water by evaporation. 

 But, from the result of many experiments, it may now be regarded as a 

 w r ell-ascertained fact that such absorption really occurs. The absorption 

 of water by the surface of the body may take place in the lower animals 

 very raj)idly. Not only frogs, which have a thin skin, but lizards, in 

 which the cuticle is thicker than in man, after having lost weight by 

 being kept for some time in a dry atmosphere, were found to recover both 

 their weight and plumpness very rapidly when immersed in water. When 

 merely the tail, posterior extremities, and posterior part of the body of 

 the lizard were immersed, the water absorbed was distributed throughout 

 the system. And a like absorption through the skin, though to a less 

 extent, may take place also in man. 



In severe cases of dysphagia, when not even fluids can be taken into 

 the stomach, immersion in a bath of warm water or of milk and water 

 may assuage the thirst; and it has been found in such cases that the 

 weight of the body is increased by the immersion. Sailors also, when 

 destitute of fresh water, find their urgent thirst allayed by soaking their 

 clothes in salt water and wearing them in that state; but these effects are 

 in part due to the hindrance to the evaporation of water from the skin. 



(6.) Regulation of Temperature. For an account of this impor- 

 tant function of the skin, see Chapter on Animal Heat. 



