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300 New Theory of Refpiration. 
up again at the fame heights, becaufe the trees are Lene 
of that mutual fhelter which they afforded to each other. 
NEW THEORY OF RESPIRATION. 
Profeffor Herholdt read lately, before the Academy of Sci- 
ences at Copenhagen, a memoir refpecting fome experiments 
made by him and M. Rafn on living animals, in order to 
difeover the mechanifm of refpiration; having in view, at the 
fame time, the cure of wounds in the breaft. The profeffor 
fhewed that the beft authors en furgery have-hitherto explained 
the mechanifn of refpiration in a manner diametrically op- 
pofite to what it really is; fo that, by applying their theory 
to the cure of wonnds in the breaft, they have followed a 
method altogether falfe. According to his experiments the 
lungs have not, as has been maintained, an expanfive force 
peculiar to them, but the movement is performed by the 
action of the diaphragm, to which fufficient attention has 
not hitherto been paid. When there are wounds in the 
breaft, the atmofpheric air enters by them on infpiring into 
the cavities of the thorax, and iffues on expiring. This has 
been proved by experiments made on horfes, dogs and cats. 
M. Herholdt and Rafn, in examining the manner in which 
the frog breathes, remarked, that this animal is without a 
diaphragm, and that its' lungs at the fame time have no ex- 
pantive force ; but that a {mall membrane, by means of which 
it can fhut its mouth hermetically, difcharges the funGtion of 
the diaphragm ; fo that, when it is prevented from fhutting 
its mouth by inferting into it a fmall rod, the animal dies in 
a few minutes, becaufe it is no longer able to breathe. When 
it is fuffered to fhut its mouth before it is entirely dead, or 
when it 1s only in a ftate of afphyxia, it foon recovers. Ifa 
frog be deprived of this membrane, by cutting it entirely off, 
or only in part, fo that its mouth can no longer be herme- 
trically fhut, it expires in a longer oy fhorter time according 
to the fize of the aperture made: on the firft view it appears 
very paradoxical that man, as well as the greater part of ani- 
mals, lofes his life by not being able to breathe when his 
mouth and nofe are fhut, and that the frog dies becaufe it 
cannat breathe when its mouth is opened. The explanation 
of - 
