for the Support of Animal and Vegetable Life. 459 



the proportion nature has assigned, it is meant to promote. I 

 have inhaled it, and given it to others, in the proportion of 36 

 to 40 parts in 100, and am fully convinced of its stimulating 

 principle. Its effects are analogous to that which is occasioned 

 by drinking fermented liquors, but, unlike intoxication, it is 

 not followed by any debility. The sens^ations are pleasant, 

 the body feels lighter, and seems to possess an increased mus- 

 cular power, which is often attempted to be exercised in some 

 ludicrous manner. When atmospheric air is inhaled by ani- 

 mals, it undergoes a decomposition in the lungs ; the oxygen 

 is retained to stimulate the fluids, and impart to the blood its 

 impetus, colour, and heat. The blood, in its circulation, is 

 evolved and distributed over the whole body, producing that 

 uniform temperature we have so much occasion to admire; 

 for, in the severest winter, the internal temperature of the 

 body is scarcely a degree lower than in the warmest summer. 

 In the summer nature throws off the excess by perspiration. 



Whilst the lungs, in their decomposition of the atmosphere, 

 retain the oxygen which is wanted for the support of life, 

 they throw off, at every expiration, the greater part of the 

 nitrogen which will not support it ; yet, mixed in the propor- 

 tion nature has assigned, the latter has the effect of neutralising 

 the properties of the former, and by its union so diluting and 

 modifying it as to prevent inspiration being over-excited; The 

 interval there is between every respiration is designed to allow 

 time for the nitrogen which the lungs discharge to ascend 

 above the head, that the same may not be repeatedly breathed, 

 but that a portion of fresh air should always be taken in. The 

 lungs give effect to this measure, by imparting such a degree 

 of heat as, by making it lighter than atmospheric air, may 

 cause it to ascend with more I'apidity. 



Of the remaining parts of the atmosphere, the hydrogen 

 and carburetted hydrogen arise from vaults, marshes, stag- 

 nant pools, &c. &c., and the carbon from combustion and the 

 animal fluids, ^from which it is discharged by expiration. 

 These gases are highly destructive to animal life ; and, though 

 they only arise in a measure from adventitious circumstances, 

 and form so small a part of the atmosphere, yet, combined 

 with the quantity of nitrogen constantly thrown off by the 

 lungs of animals, they would soon render the air destructive to 

 animal life, were not this effect so admirably counteracted by 

 the Creator, whose infinite comprehension foresaw the ten- 

 dency of every law it was about to establish, and whose wis- 

 dom provided for every contingency that could arise from the 

 amalgamation of properties negative and destructive. The 

 system adopted was by creating in plants also the power of 



