EFFECTS OF RESPIRATION ON THE AIR. 393 



bonic acid in the expired air has been found to be unusually great in the 

 Exanthemata, and in chronic Skin-diseases (Macgregor) j 1 and it has been 

 stated to.be diminished in Typhus (Malcolm). 2 Thus, the average propor- 

 tion in health being about 4.3 per cent. (Vierordt), it has been seen at 8 per 

 cent, in confluent Small-pox, at 5 per cent, in Measles, and at 7.2 per cent, 

 in a severe case of Ichthyosis which terminated fatally ; whilst in Typhus 

 the percentage has been found to range from 1.18 to 2.50. But these state- 

 ments do not indicate the total quantity exhaled in each case. The remark- 

 able increase of the exhalation in cases of Chlorosis has been already noticed ; 

 in four cases recorded by Hannover, the hourly expiration was 123.6, 118.6, 

 116.9, and 106.3 grains ; the absolute quantity diminishing as the respira- 

 tions increased in rapidity. In chronic diseases of the respiratory organs, as 

 might lie anticipated, the amount of Carbonic acid exhaled undergoes a sen- 

 sible diminution (Nysten 3 and Hannover). 4 Further researches are much 

 needed on this subject ; but, for obvious reasons, they cannot be readily 

 made in severe forms of disease. The greater part, if not the whole, of the 

 Oxygen absorbed in respiration is again eliminated in combination with 

 Carbon as Carbonic acid. In the original experiments of Lavoisier on 

 Guinea-pigs, 81 per cent, of the Oxygen thus reappeared, the remaining 19 

 per cent., which disappeared, were believed by him to unite with hydrogen 

 to form water. The results of Reguault and Reiset's experiments on various 

 animals mammals, birds, reptiles, insects, and annelids 5 were almost pre- 

 cisely the same ; the general average being, that for each kilogramme of 

 weight of the animal, there were absorbed per hour 3.0219 grammes of oxy- 

 gen ; whilst there were exhaled 3.2544 grammes of Carbonic acid ; and they 

 found that 80.5 per cent, of the Oxygen absorbed was discharged in combi- 

 nation with the Carbon, but considerable variations occurred connected with 

 the nature of the food, a larger proportion of the Oxygen absorbed being 

 combined with Carbon when the food was rich in Carbon, 6 amounting in 

 Ruminants to about 100 per cent. Pettenkofer and Voit 7 also found the 

 proportion of Oxygen eliminated in the form of Carbonic acid varied, in a 

 large dog, from 52.4 to 148.2, according as he was kept altogether without 

 food, or was fed upon a mixed diet of meat and sugar. 



The table (p. 391) shows a remarkable excess of the diurnal against the 

 nocturnal elimination of Carbonic acid, especially after work, and a corre- 

 sponding increase in the percentage of the absorbed Oxygen which is thus 

 discharged. On the other hand, the absorption of Oxygen appears to take 

 place most energetically during the night, whilst, taking the whole period of 

 24 hours into consideration, it appears that in both sets of experiments from 

 94 to 98 per cent, of the oxygen absorbed is eliminated in combination with 

 Carbon as Carbonic acid. * In other and still more recent researches, the 

 same difference was not observed 8 between the day and night absorption of 

 Oxygen and elimination of Carbonic acid, and no definite statement as to 

 the'exact proportion can therefore as yet be made. The elimination of Urea 



1 Edinb. Monthly Journal, 1843. - Report of Brit. Assoc., 1813, p. 87. 



3 Pvecherches de Physiologic et dc Chimie Pathologique, 1811. 



4 De Qnantitate relaliva et absoltita Acidi Carbonici ab Homine Sano et zEgroto 

 exhalati, 1843. 



6 See Longet's Physiologie, 1861, t. i, p. 556. 



* Kowalewsky, Arbeiten aus der Physiol. Anstaltzu Leipzig, 1807, p. 33, was only 

 able to obtain about 50 per cent, of the oxygen absorbed in the carbonic acid exhaled, 

 by means of his new apparatus, in rabbits fed on cabbage leaves. 



' 7 Prof Haughton's Address, On the Relation of Food to Work, Brit. Med. Asso- 

 ciation Meeting, August, 1868. 8 Op. cit., February, 1867. 



26 



