THE EARTH. 



93 



That air which is so necessary to the life 

 of vegetables, is still more so to that of ani- 

 mals ; there are none found, how seemingly 

 torpid soever, that do not require their need- 

 ful supply. Fishes themselves will not live 

 in water from whence the air is exhausted ; 

 and it is generally supposed that they die in 

 frozen ponds, from the want of this necessary 

 to animal existence. Many have been the 

 animals that idle curiosity has tortured in the 

 prison of a receiver, merely to observe the 

 manner of their dying. We shall, from a 

 thousand instances, produce that of the viper, 

 as it is known to be one of the most vivacious 

 reptiles in the world ; and as we shall feel 

 but little compassion for its tortures. Mr. 

 Boyle took a new-caught viper, and shutting 

 it up into a small receiver, began to pump 

 away the air." " At first, upon the air's being 

 drawn away, it began to swell ; some time af- 

 ter he had done pumping, it began to gape, 

 and open its jaws ; being thus compelled to 

 open its jaws, it once more resumed its for- 

 mer lankness ; it then began to move up and 

 down within, as if to seek for air, and after a 

 while foamed a little, leaving the foam stick- 

 ing to the inside of the glass ; soon after, the 

 body and neck grew prodigiously tumid, and 

 a blister appeared upon its back; an hour 

 and a half after the receiver was exhausted, 

 the distended viper moved, and gave manifest 

 signs of life ; the jaws remained quite distend- 

 ed ; as it were from beneath the epiglottis, 

 came the black tongue, and reached beyond 

 it; but the animal seemed, by its posture, 

 not to have any life ; the mouth also was 

 grown blackish within ; and in this situation 

 it continued for twenty-three hours. But upon 

 the air's being re-admitted, the viper's mouth 

 was presently closed, and soon after opened 

 again ; and for some time those motions con- 

 tinued, which argued the remains of life." 

 Such is the fate of the most insignificant or 

 minute reptile that can be thus included. 

 Mites, fleas, and even the little eels that are 

 found swimming in vinegar, die for want of 

 air. Not only these, but the eggs of these ani- 

 mals, will not produce in vacuo, but require 

 air to bring them to perfection. 



As in this manner air is necessary to their 



Boyle'* Physico-Mechan. Exper. passim. 



subsistence, so also it must be of a proper 

 kind, and not impregnated with foreign mix- 

 tures. That factitious air which is pumped 

 from plants or fluids, is generally, in a short 

 time, fatal to them. Mr. Boyle has given us 

 many experiments to this purpose. After 

 having shown that all vegetable, and most 

 mineral substances, properly prepared, may 

 afford air, by being placed in an exhausted 

 receiver, and this in such quantities, that 

 some have thought it a new substance, made 

 by the alteration which the mineral or plant 

 has undergone by the texture of its parts 

 being loosened in the operation having 

 shown, I say, that this air may be drawn in 

 great quantities from vegetable, animal, or 

 mineral substances, such as apples, cherries, 

 amber burnt, or hartshorn b he included a 

 frog in artificial air, produced from paste ; in 

 seven minutes space it suffered convulsions v 

 and at last lay still, and being taken out, re- 

 covered no motion at all, but was dead. A 

 bird, inclosed in artificial air, from raisins, 

 died in a quarter of a minute, and never stir- 

 red more. A snail was put into the re- 

 ceiver, with air of paste ; in four minutes it 

 ceased to move, and was dead, although it had 

 survived in vacuo for several hours : so that 

 factitious air proved a greater enemy to ani- 

 mals than even a vacuum itself. 



Air also may be impregnated with fumes 

 that are instantly fatal to animals. The 

 fumes of hot iron, copper, or any other heated 

 metal, blown into the place where an animal 

 is confined, instantly destroy it. We have al- 

 ready mentioned the vapours in the grotto 

 Del Cane suffocating a dog. The ancients 

 even supposed, that these animals, as they al- 

 ways ran with their noses to the gr.ound, were 

 the first that felt any infection. In short, it 

 should seem that the predominance of any 

 one vapour, from any body, how wholesome 

 soever in itself, becomes infectious ; and that 

 we owe the salubrity of the air to the variety 

 of its mixture. 



But there is no animal whose frame is 

 more sensibly affected by the changes of the 

 air than man. It is true, he can endure a 

 greater variety of climates than the lower 

 orders generally are able to do; but it is 



. b Boyle's Physico-Mechan, vol. ii. p. 598. 

 Y* 



