520 LIQUID PARTS OF ANIMALS. 



tion amounts to 24 ounces in twenty-four hours. According to Keil 

 it is rather more than 31 ounces, or very nearly 2 Ibs avoirdupois.* 

 Dr Bryan Robertson and Mr Rye made a similar set of experi- 

 ments in Ireland, as did Dr Lining in Carolina. But these expe- 

 rimenters neglected to distinguish the matter perspired through 

 the skin from what was thrown out by the lungs. 



Lavoisier and Seguin were the first persons who attempted to 

 ascertain the amount of the matter perspired by the skin, and to 

 separate it from what was thrown out by the lungs. A bag com- 

 posed of varnished silk, and air-tight, was procured, within which 

 Seguin, who was usually the subject of experiment, was enclos- 

 ed ; every part of the body being included. There was a slit 

 in the bag opposite to the mouth, and the edges of the slit were 

 accurately cemented round the mouth by means of a mixture of 

 turpentine and pitch. Thus everything emitted from the body 

 was retained in the bag, except what made its escape from the 

 lungs during expiration. By weighing himself in a sensible ba- 

 lance before the experiment began, and again after he had been 

 for some time enclosed in the bag, the difference of weight 

 gave the matter exhaled from the lungs. While the weight of 

 the bag before and after the experiment gave data for deter- 

 mining the quantity of matter exhaled from the skin during the 

 same length of time. The following facts were ascertained by 

 these experiments : 



1. The maximum of matter perspired in a minute amounted 

 to 26-25 grains troy ; the minimum to 9 grains ; which gave 

 17-63 grains at a medium in the minute, or 52'89 ounces in 

 twenty-four hours. This is very near the quantity stated by 

 Sanctorius as the result of his numerous experiments. 



2. The quantity perspired is increased by drink ; but not by 

 solid food. 



3. Perspiration is at its minimum immediately after a repast. 

 It reaches its maximum during digestion. f 



Mr William Cruikshanks published a work on insensible per- 

 spiration in 1795. He seems to have been the first person who 

 thought of collecting the matter perspired so as to be able to 

 judge of its nature. He inclosed his hand within a glass vessel 

 and luted its mouth to his wrist by means of a bladder. The 

 interior surface of the glass became gradually dim, and drops of 



* See Quincy's Medic ina statica, p. 323. 

 t Fourcroy, ix. 276, English translation. 



