188 



who has lately repeated these experiments in Ameri- 

 ca, found> that the gases collected by holding the 

 arm in an inverted glass-vessel filled v/ith water, 

 differed in no considerable degree from those which 

 had been previously obtained from the water. These 

 facts altogether forbid our drawing any conclusion 

 in favour of an aerial transpiration by the skin, from 

 the mere circumstance of air being separated by the 

 body when it is immersed in certain kinds of water, 

 149. But Mr Abernethy supports the opinion of 

 an aeriform perspiration by the skin on other grounds, 

 maintaining, that carbonic acid is given out as well 

 when the hand is plunged in a jar of mercury, or is 

 immersed in any kind of air, as when it is placed in 

 contact with oxygen gas *. After detaching the ad- 

 hering air from the surface of his hand, by moving 

 it for ten minutes in mercury, he introduced it with- 

 in a jar filled with that fluid, the thermometer 

 standing at about 6O. Minute air bubbles rose at 

 first to the top of the fluid, but more slowly after- 

 wards ; and in an hour, when the hand was with- 

 drawn, the air collected was equal in bulk to one 

 scruple of water. In sixteen hours, it equalled half 

 an ounce ; and of this, two-thirds were attracted by 

 lime water, and the remainder did not diminish on 

 mixture with nitrous gas : whence he concludes, 

 that it consisted of carbonic acid and nitrogen gas^ 

 and that these gases were perspired by the skin. 

 The small quantity of air separated in this experi- 

 ment, during sixteen hours, is itself a proof that this 



* Essays, Surgical, &c. p. 121, 122, 



