Theories and Experiments 479 



The enormous quantity of carbonic acid found by Vivenot (he 

 says) results from making the expirations too strong; in fact, taking 

 his figures, we find that the pulmonary ventilation for 24 hours at 

 normal pressure is 21,111.2 liters, and in compressed air 19,745.5 

 (Panum in one experiment gets 1152 liters for himself at normal 

 pressure). In respiration so greatly forced as that, he finds a produc- 

 tion of carbonic acid of 1300 grams in normal air and of 1449.5 gm. in 

 compressed air (Panum gets 816.2 gm. in himself). 



As to him, he made his analyses on 60 or even 120 liters of air 

 expired in a spirometer at different periods in the experiment. 

 Moreover, he does not give very clear specifications of the manner 

 in which he carried out this experiment; I can find only that the 

 compression was 24 centimeters: 



I have found no trace in my experiments of this increase in the 

 production of carbonic acid after the air treatments, of which Vivenot 

 speaks .... I consider the opinion of Vivenot a mistake, because his 

 method had no solid basis and could not be used to estimate the 

 quantity of air which passes regularly through the lungs in a given 

 time, with quiet and natural respiration; his respiratory rhythm was 

 forced, not natural .... 



If we compare in. my tables the cases in which equal volumes of 

 compressed air and normal air were breathed, we find that the 

 quantity of carbonic acid exhaled has increased absolutely and rela- 

 tively in compressed air. But if we compare the cases where there 

 was the same volume of air, when reduced to the same pressure, 

 breathed in free air" or under the bell, we see that a little less carbonic 

 acid was produced in the compressed air than at normal pressure. In 

 other words, the quantity of carbonic acid exhaled increases during 

 respiration in compressed air because of the increase in the mass of 

 air which passes through the lungs, as a result of this pressure, but 

 in a proportion a little less than the latter. (P. 143-146.) 



But this is exactly the result which Vivenot reached, in spite 

 of the faulty method which he had used. Panum is surprised at 

 this agreement: 



The experiments of Regnault and Reiset, in which the respiration 

 of an air with greater oxygen content had not brought a greater 

 excretion of carbonic acid, seemed to prove a priori that the same 

 would be true in compressed air. Yet my results were the same as 

 those of Vivenot, and were contrary to my expectation, which makes 

 them all the more convincing. 



What causes such a difference between the respiration in air with 

 high oxygen content at normal pressure, and that in normal air at 

 higher pressure? 



We might ask whether it is the oxygen chemically united with 

 the corpuscles of the blood, or that which is simply absorbed, which 

 in one case oxidizes more energetically than in the other. If one 

 breathes superoxygenated air at normal pressure, then the increased 



