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in the contact of the air. But any that be the state of the carbonic acid in the blood, or the hypothesis of Magnus' simple dissolution be adopted, or the one of Liebig in alkaline bicarbonates, they are always accountable the chemical phenomena of the breathing, although the one of Magnus facilitates more the explanation, because that now they enter in the domain of the physical laws of the absorption of the gases by the liquids and in the empire of the chemical affinities.

All the liquids have the property of absorbing the gases with which they are put in contact, and the saturation degree varies according some and other, nor for this absorption to be verified, it is indispensable that the contact is immediate.

But the liquids don't conserve the gases of which they are saturated in all the circumstances. It is necessary that its temperature doesn't rise, the pressure doesn't diminish, and that this one be exercised by an identical gas to the one that saturates them; if this comes to change, under the influences of that which substitutes it, a great portion of the first is expelled, and of the second a part is absorbed. It is for that that a current of gas hydrogen or of gas nitrogen through the blood determines the expulsion of the carbonic acid gas, and it is for that same reason that the frogs give the same carbonic acid, after the inhalation of the first two gases, as with the atmospheric air, and what happens in the frogs it has room in all the animals; in some through the skin, in others through the gills, and in those provided of lungs, as the man, through the very tenuous membranes, that divide the two fluids in those organs, because that the thickness of the walls of the last lung very small arterial branches is from 0,005 to 0,010 of line, and the diameter of those branches from 0,0002 to 0,0003 and even in the man as well as it is undeniable the exhalation of the carbonic acid by the skin, it is also it the absorption of the oxygen for the same road, as it proves the experience referred by Burdach in which it was discovered the disappearance of the oxygen of the bell, that contained him, and where had been introduced the hand of a subject through the mercury over which the bell rested, and this explains the rubefaction constant in the cheeks of the comsumptive ones, providing the organization in that point, in a tiny part, the lack of hematosis in the lungs.

But with relationship to the state of the carbonic acid in the blood, the last supposition, that is the one of combination, is very false, already because it is indubitable that in the lungs is that the maximum part is made of the sanguinification, and already because the breathing in the hydrogen in the frogs gives in the same way carbonic acid, in spite of there not being oxygen there to go superoxidate the organic substances of the blood, and to determine conseguintemente the formation of the organic acid to decompose the alkaline bicarbonates. Reasons previously presented enfeeble the supposition of the decomposition of the bicarbonates by the contact of the air in the lungs, for its sequent exhalation, and for that, not only by exclusion, but also