360 RESPIRATION. 



gases occurring in the lungs. There must, however, be a certain 

 limit for every organism, beyond which the absorption of oxygen 

 and the excretion of carbonic acid cannot pass. We have already 

 seen (pp. 248-268) that the absorption of nutrient matter from the 

 intestinal canal can only be carried to a certain extent, and we 

 have further convinced ourselves that notwithstanding this limita- 

 tion of resorption, a far larger quantity of nutrient matters may 

 enter into the mass of the fluids than is necessary for the main- 

 tenance of the vital functions ; while we finally observe that this 

 excess of absorbed food, when it consist of nitrogenous matters, is 

 very rapidly decomposed in the blood, and that under these con- 

 ditions large quantities of urea, far exceeding the normal mean, are 

 excreted. But as we have already shown that only a fractional 

 part of the albuminates is eliminated with the urine, while another 

 portion is separated through the lungs, as water and carbonic acid, 

 there can be no doubt that the pulmonary exhalation, as well as the 

 other excretions, is correspondingly augmented after an excessive 

 use of nutrient substances. All the experiments which have 

 hitherto been made in reference to the excretion of carbonic acid 

 in animals that have either been highly fed, or have been artificially 

 fattened, confirmed the above proposition. As we purpose revert- 

 ing at a future page to this subject, we will only adduce a couple 

 of experiments made by C. Schmidt* on one and the same cat. 

 When this animal was taking 142*41 grammes of flesh in the 24 

 hours (a quantity which was shown by numerous experiments to 

 be sufficient to maintain the full strength and ordinary weight of the 

 animal), it absorbed 60*14 grammes of oxygen, and exhaled 65*60 

 grammes of carbonic acid, together with 30'88 grammes of water ; 

 whilst during the consumption of 247*32 grammes of flesh it 

 absorbed 103*84 grammes of oxygen, and expired 113*52 grammes 

 of carbonic acid and 47'86 grammes of water. Regnault and 

 Reiset's experiments also exhibit similar results in the case of the 

 herbivora, for we there meet with several cases in which the excess 

 of the absorbed carbo-hydrates may be distinctly recognised by the 

 proportion existing between the absorbed oxygen and that which 

 is excreted with the carbonic acid, this being in many cases as 

 100 : 95, or even as 100 : 997? consequently nearly the ratio 

 (namely as 100 : 100) which accords with the requirements of 

 theory after the use of pure sugar or starch. 



The above circumstance leads us to a point, which although it 

 will be considered with all the attention which it deserves under 



* Op. cit. 



