SECT. IV. PHYSIOLOGY. 29 
expansion of the skin which takes place during 
immersion, is by far the most effectual method 
of expelling the condensed perspiration from the 
cutaneous exhalants, and preserving the pliability, 
health, and beauty of the dermoid system. 
. L. The sweat is chiefly composed of water and 
acetous acid, but like other secretions its com- 
position is very changeable. 
~ Li. Physiologists have laboured hard to establish 
the quantity of perspiration by the skin; Keil 
reckons the mean quantity for this country at 
thirty ounces in twenty-four hours. But in 
tropical countries it cannot fall much short of five 
pounds, from the quantity of liquids requisite to 
preserve health. 
Li. Strong mental affections, especially those 
of a disagreeable nature, often alter the irritability 
of the skin in a very short time. Dr. Alibert 
relates the case of a man who was attacked on 
the spot where he stood, with herpes, from seeing 
his master dragged to the scaffold by the revolu- 
tionary mob. I extract the following case of 
tinea asbestina from the same author: “ This 
woman experienced the most bitter affliction, 
owing to the ill treatment which she received 
from her husband and children. When she was 
a little tranquil, the parts affected furnished an 
abundant suppuration, the crusts fell off, and the 
“~~ tinea seemed healing. When, on the contrary, 
