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THE ZOOLOGIST. 
THIRD SERIES. 
Vou. X.] AUGUST, 1886. [No. 116. 
SOME OF THE WAYS IN WHICH ANIMALS BREATHE.* 
By Prorrssor F. Jerrrey Betz, M.A. 
Ir we consider the essential points, as distinguished from the 
special or accessory methods, of human respiration, we shall 
most easily get at the central and important facts. Minute by 
minute we take into our lungs a certain quantity of what we 
call air, and as often we get rid of what we call air too. But 
between what we inspire or take in, and what we expire or give 
out, there are certain differences; differences which, not detectable 
on a breezy common, soon become unpleasantly obvious in an 
ill-ventilated or overcrowded room. In other words, we get rid 
of something which we had best not take in again; that some- 
thing you know is the gas which is called carbonic acid; and, 
though carbonic acid is quite in its place, and indeed very 
pleasant, in seltzer-water or champagne, it is not to be recom- 
mended as a ‘“‘respiratory medium”’; a little too much of it 
produces headache and malaise, still more of it (as in suicides 
by charcoal poisoning) produces death. 
Air, as you know, is chiefly composed of oxygen and nitrogen, 
and, speaking generally, there are 21 parts of the former to 79 
of the latter gas in every 100 parts of atmospheric air; if you 
breathe pure oxygen you become exhilarated, and if you take it 
* An abstract of one of the “‘ Davis Lectures,” delivered at the Zoological 
Society’s Gardens, July 1st, 1886. 
ZOOLOGIST.—AUGUST, 1886. Qa 
