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they recognized to contain the veined blood alkaline sub-carbonate in larger amount than the arterial one. Picked these data, with them applied, they believed to have explained the breathing. So the great contact of the air with the blood in the lung formed not only some carbonic acid and water, but also improving some organic substances, and decomposing other, made to appear the acetic acid, that, combining with the alkali of the sub-carbonate, it allowed the exhalation of the carbonic acid. The difficulty of solving the problem of the hematose, proven by the same multiplicity of the theories, some so diverse of other in its bottom, came surely of the lack of perfect knowledge of the composition of the fluid the to be arterialized, and also of the phenomena of the organic decomposition, that completes the assimilation. With effect, the need to explain the emergence of the exhaled carbonic acid, was the great rock of the breathing, believing the physiologists that its formation was owed to the oxygen immediately inspired: therefore, to discover the incognito of the problem, it is of obvious convenience to know previously: first, if the carbonic acid gas and the gas oxygen exist in the blood; second, if only the atmospheric air or if other gases can also make to appear the carbonic acid; third, if the breathing of the animals of cold blood in any other one gas can give that product. The first requirement receives from the experience an affirmative answer. With the help of the pneumatic machine, Voguel, Brandishes and Home demonstrated the presence of the carbonic acid in the veined blood. By its agitation with any other gas, or crossing it with a gaseous current of nitrogen or hydrogen, for instance, as made Hoffman and Steven, it is obtained the carbonic acid. Finally Magnus' experiences evidenced its presence in the veined blood, as well as in the arterial, and also of the oxygen in both, but in very larger amount in the last. The mentioned experiences of Hoffman and Steven give affirmative solution of the second requirement equally. The third seem to have an equal one in a long series of experiences.

Edwards immersed a frogs in gas hydrogen, where it conserved it for eight and a half hours; for that time she exhaled 1,49 of cubic inch; what seems exaggerated, because in the same space the exhalation is smaller in the atmospheric air. Collard of Martigny, immersing the frogs in nitrogen, previously having the care of compressing their lungs and the larynx, and changing of two in two hours the nitrogen of the experience, they obtained a little smaller result, because among other, one, conserved in the nitrogen by eight and a half hours, exhaled 1,31 of cubic inch of carbonic acid. Similar experiences of Bergeman and Muller discovered the exhalation of the carbonic acid, although in smaller amount. They purified the hydrogen, either with the alcohol, or with the caustic potash, they compressed the lungs of the frogs before, and they put them in the hydrogen contained in a bell resting on mercury; and constantly there was exhalation. - One was able