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this could be achieved, was a matter for long and untiring experiments and trials and repeated failures. But Chemistry was at last applied to the case, and instead of the troublesome operation of perpetually changing the water, ever in dread that a case similar to that we have quoted above might occur, the long sought end was attained; by what is called compensation, animals may be kept alive for an indefinite period,—viz.: by thoroughly understanding the relations between animal and vegetable life on the principles of Priestley, followed up by Ingenhouss, and "finally adapted to the present purpose by Mr. Ward, the inventor of the glass cases which bear his name, Johnston, the learned author of Histories of the "British Zoophytes," "Sponges," &c, Warrington and Gosse. It was Mr. Bowerbank, however, who gave the hint to the Secretary of the Regent's Park Gardens, from which arose the beautiful tanks which are now in full operation there. We have often before had this process of respiratory interchange explained, but who has brought it so vividly before us, as our often quoted friend and companion (his charming writings have made him so,) Mr. Lewes. "Let us stand apart," he says, "and contemplate this marvel no longer as an animal function, but rather as a planetary phenomenon; let us endeavour to picture to ourselves the silent creative activity everywhere dependent on this interchange. The forests, the prairies, the meadows, the cornfields, and gardens,—the mighty expanse of plant-life covering mountain and valley—these subsist on the carbonic acid which is exhaled from the lungs and bodies of animals.
