326 



RESPIRATION. 



found the maximum quantity of carbonic acid 

 gas in 10,000 parts of atmospheric air to be 

 6'2, the minimum 3'7, and the average 4'9 or 

 nearly 1 part, by volume, of carbonic acid gas 

 in 2000 parts of atmospheric air. Results 

 similar to those procured by Saussure, who 

 experimented at Geneva, have been obtained 

 by Boussingault* and Thenardf at Paris, 

 Brunnerf at Berne, and Verver$'at Gro- 

 ningen in Holland, so that we have the 

 strongest grounds for believing in their general 

 accuracy. The variable quantity of watery 

 vapour that exists in the atmosphere must 

 also be taken into account in examining the 

 function of respiration. A quantity of ammo- 

 nia, so small however that its usual pro- 

 portion cannot be ascertained, is constantly 

 present in the atmospheric air, which, when 

 it descends to the earth dissolved in water, 

 serves, according to Liebig, an important 

 purpose in the nutrition of vegetables. There 

 are, besides the above substances, numerous 

 others in the gaseous form, exhaled from the 

 surface of the earth, too minute to be detected 

 by analysis, but sometimes recognised by their 

 effects upon the living organism. No doubt 

 the miasmata and effluvia, which can inflict 

 such disastrous evils on the human race, are 

 diffused through the atmospheric air. 



Though the proportions of the three gases, 

 viz. nitrogen, oxygen, and carbonic acid, 

 usually regarded as forming the constituent 

 parts of our atmosphere, are not quite uniform 

 at all times and in all places, chiefly from local 

 disturbing causes, yet these differences are to 

 a small extent, when its free circulation is 

 permitted. Dalton || maintained, that in ele- 

 vated regions the proportion of oxygen to 

 azote is somewhat less than at the surface of 

 the earth; but this is not confirmed by the 

 more recent experiments of Dumas, Boussin- 

 gault, and Brunner. In the experiments of 

 Lewy If and Morren **, the composition of 



* Anuales de Chimie et de Phvsique, torn. x. 

 p. 456. 1844. 



f Referred to in opus supra citatum, torn. x. p. 463. 

 1844. Thenard's experiments were made prior to 

 those of Saussure. 



J Opus supra cit. torn. iii. p. 313. 1841. 



Referred to in opus supra cit., torn. x. p. 462. 

 1844. 



|| London and Edinburgh Philosophical Magazine 

 and Journal of Science, vol. xii. p. 406. 1838. 



^f Annales de Chimie et de Physique, torn. viii. 

 p. 425. 1843. Lewy found the quantity of oxy- 

 gen in the air near the surface of the North Sea 

 on an average 22'6 by weight in the 100 of air, 

 while the air over the land contained 23 of oxygen 

 in the 100. 



** Annales de Chim. et de Phys., torn. xii. p. 5. 

 1844. Morren states that the air resting upon the 

 surface of the sea, in calm weather, may contain 

 from 23 to 24 parts, by volume, of oxygen instead of 

 20-8, the usual quantity ; and this increased quan- 

 tity of oxygen, under the circumstances mentioned, 

 is connected, as we shall see immediately, with the 

 action of the marine vegetation upon the atmospheric 

 air. The experiments of Lewy and Morren are not 

 contradictory ; for in those of the former the air was 

 taken from the surface of the deep sea at some dis- 

 tance fi-om the shore, and in those of the latter the 

 air analyzed had been resting for some time over 



the air near the surface of the sea differed in 

 its amount of oxygen from that over the land. 

 Saussure detected a somewhat smaller quan- 

 tity of carbonic acid gas in the air during the 

 clay than during the night *, and a larger 

 quantity in the air of the town of Geneva 

 than in that taken in the country three-fourths 

 of a league distant, in the proportion of 100 

 to 92 ; and Boussingault and Lewy, in their 

 later experiments, observed a similar dif- 

 ference between the air taken from the densest 

 parts of Paris and that of the country, f 

 Lewy detected a considerable increase of 

 carbonic acid gas, no doubt of volcanic origin, 

 in the air of Guadeloupe, but without any 

 diminution in the usual relative proportions 

 of the oxygen and nitrogen. J As a portion 

 of the oxygen of the atmospheric air is com- 

 bined with carbon to form carbonic acid gas 

 in the respiration of animals, in ordinary 

 combustion, and in numerous other chemical 

 processes going on at the earth's surface, it is 

 obvious that when individuals of the human 

 species are surrounded by a limited quantity 

 of air which is not renewed so rapidly as it is 

 vitiated by respiration, the proportion of oxy- 

 gen gas will be diminished and the carbonic 

 acid increased, and this the more rapidly if 

 any other process of deoxidation of the con- 

 fined air be at the same time in operation. 

 Dalton analyzed the air of a room where 50 

 candles had been kept burning and 500 people 

 had been collected for two hours, and found 

 that it contained 1 per cent, of carbonic acid 

 gas. Leblanc made a number of analyses 

 of the air taken from the rooms of some of 

 the public buildings in Paris. || He collected 

 some of the air of one of the wards of La 

 Pitie, the area of which was 70,632 cubic feet, 

 containing 54 patients, after it had been shut 

 during a whole night, and procured from it 3 

 parts of carbonic acid gas, by weight, in the 

 1000, or about 5 times as much carbonic acid 

 as is usually present in the atmosphere.lT The 

 oxygen gas had suffered a corresponding 

 diminution. In one of the sleeping apart- 

 ments of the Salpetriere, the carbonic acid gas 

 amounted to 6 parts, by weight, in the 1000 

 parts of the contained air, and in another 

 sleeping apartment to 8 parts in the 1000.** 

 In the Amphitheatre of Chemistry at the 

 Sorbonne, the air collected at the end of the 

 lecture furnished 10'6 of carbonic acid, by 



pools of sea-water abounding in alga?, exposed to 

 the sun's rays. 



* Boussingault (opus cit. torn. x. pp. 464, 465) 

 obtained similar results ; but he admits that more 

 extended observations are required on this point. 



f Annales de Chim. et de Phvs., torn. x. p. 470. 

 1844. 



J Idem opus, torn. viii. p. 450. 1843. 



London and Edinburgh Philos. Mag., vol. xii. 

 pp. 405, 406. 1838. 



|| Annales de Chim. et de Phys., torn. v. p. 223. 

 1842. 



^f If the usual quantity of carbonic acid in the 

 atmosphere be from 4 to 6 in the 10,000 parts by 

 volume, that is equal to from 6 to 9 of carbonic acid 

 gas by weight. 



** 'Opus cit, p. 233. 



