RESPIRATION. 



327 



weight, in the 1000. The air collected in the 

 pit of the Opera Comique a short time before 

 the termination of the performance contained 

 2 - 3 ; while in another experiment the air 

 from one of the boxes contained 4'3, by weight, 

 of carbonic acid gas in the 1000. In one of 

 the stables at the Ecole Militaire, the air 

 collected after it had been kept closed for a 

 night yielded 1'05 in the 100 ; and the air 

 from another which was better ventilated 

 yielded about 2 parts in the 1000, by weight.* 

 If, according to the opinion of Leblanc and 

 others, carbonic acid gas exerts a prejudicial 

 effect upon the vital actions in the human 

 species when it has accumulated to the extent 

 of 1 per cent, in the air to be breathed, the 

 above facts, to which many others might 

 readily have been added, point out the im- 

 portance of securing sufficient ventilation both 

 in our private and public buildings. 



As the gases held by water in solution sup- 

 ply the means of aquatic respiration to many 

 animals and plants, a knowledge of the quan- 

 tity and composition of these gases is also 

 necessary for the full comprehension of the 

 function of respiration. Humboldt and Gay 

 Lussac state that the water of rivers, and dis- 

 tilled water well aired, hold in solution about 

 2* 7 th of their volume of air composed of about 

 32 of oxygen and 68 of azote, by volume.f 

 Morren J concludes from his experiments that 

 sea-water contains in solution between ^th 

 and -^th of its volume of air, a quantity sen- 

 sibly less than that obtained from fresh-water, 

 which usually contains from -g^th to ^V^ n > or 

 even J v th of its volume. He found that the 

 air obtained from fresh-water under ordinary 

 circumstances, whether distilled and again 

 perfectly aerated, or the limpid water of a 

 moderately rapid stream, contains 32 parts of 

 oxygen, and from 2 to 4 of carbonic acid, by 

 volume, in the 100; while the air obtained 

 from sea-water yielded 33 of oxygen and 

 from 9 to 10 of carbonic acid in the 100. The 

 relative proportion of the gases obtained both 

 from fresh and sea- water varies considerably 

 under certain conditions. In fresh-water ponds 

 abounding in plants or green animalculse, and 

 in shallow parts of the sea, where numerous 



* According to the experiments of M. Lassaigne 

 (Comptes Rendus, 13th Juillet, p. 108. 1846) the 

 carbonic acid gas, formed by respiration in apart- 

 ments where the ventilation is very imperfect, is not 

 confined to the parts nearest the floor, but is diffused 

 nearly in equal proportions through every portion 

 of the mass of air in the apartments. 



f Journal de Physique et de Chimie, par Dela- 

 mitherie, torn. Ix. p. 158. The percentage of oxygen 

 from the air of water of the Seine was 31*9 ; of dis- 

 tilled water which had again absorbed air, 32*8 ; 

 and of rain water, 31'0. (p. 159.) 



J Annales de Chim. et de Phys., torn. xii. 1844. 



M. Lewy (Comptes Rendus, 28th Sept. 1846) 

 states that, in his experiments, one litre (61-027 

 cubic inches English) of Seine water yielded about 

 40 cubic centimetres (2-440 cubic inches) of air, and 

 the same quantity of water from the ocean furnished 

 only 20 cubic centimetres (1-220 cubic inches). The 

 water of the ocean, in consequence of the salts it 

 holds in solution, absorbs much less atmospheric 

 air than fresh water. 



algae flourish, the proportion of oxygen gas 

 may be considerably increased during sun- 

 shine, especially if the water be at the same 

 time still. Morren analyzed, in a bright day 

 in July, the gas dissolved in the water of 

 a fish-pond of a green colour, chiefly from 

 the numerous animalculae it contained, and 

 found in that procured in the morning 25, at 

 mid-day 48, and in the evening as much as 6 1 

 of oxygen in the 100 parts.* Similar changes, 

 but to a less extent, were detected by Morren 

 in the air of sea-water, and they are chiefly 

 dependant upon the action of the algse. In 

 one experiment, performed on a fine sunny 

 day, when the sea was at the same time calm, 

 the air obtained from the water yielded 40 per 

 cent, of oxygen in the early part of the day, 

 and 53'6 in the evening. The total quantity 

 of air obtained from both kinds of water varied 

 at different times of the day ; and its increase 

 was chiefly dependant upon the addition of 

 oxygen, the carbonic acid at the same time 

 suffering a decrease, but not in the same pro- 

 portion, while the nitrogen f seemed to suffer 

 little change. This increase of oxygen will 

 partly contribute to the supply required for 

 the respiration of the numerous aquatic ani- 

 mals which usually frequent the localities 

 where it is evolved, and be partly given off to 

 the superincumbent air, and thus assist in 

 maintaining the purity of the atmosphere. 



Notwithstanding the large quantity of oxy- 

 gen daily removed from the atmosphere by the 

 respiration of animals and other causes, yet 

 from the great extent of the atmosphere, and 

 the rapid mixture of its different parts, a long 

 period of time must necessarily elapse before 

 it suffers any marked deterioration, even were 

 there no compensating operation in the vege- 

 table kingdom. The oxygen gas in the atmo- 

 sphere is equal in weight to a column of 7*8 

 feet of water pressing upon every part of the 

 earth's surface : and it has been stated that it 

 would require 10,000 years, supposing the 

 earth peopled with 1,000,000,000 of men to 

 produce a perceptible effect upon the eudio- 

 meter of Volta, even though vegetable life 

 was annihilated ; and that to suppose all the 

 animals on the surface of the earth could by 



* Opus cit. p. 9. Wohler (Poggendorff 's Annalen 

 der Physik und Chemie, band Ivii. S. 308. 1842) 

 analyzed the gas exhaled from the greyish yellow 

 mass, consisting in a great measure of living infu- 

 soria mixed with some confervas, which collects in 

 a salt spring at Rodenberg in Hesse, and found it to 

 be composed of 51 per cent, of oxygen, and 49 of 

 nitrogen. 



f M. Lewy (Comptes Rendus, 28th Sept. 1846) 

 has observed similar changes, but not to the same 

 extent, in the relative proportions of oxygen and 

 carbonic acid in the air of sea- water under the cir- 

 cumstances mentioned by Morren. According to 

 the results of Lewy, the waters of the ocean contain 

 a small quantity cf sulphuretted hydrogen gas, ap- 

 parently evolved from the bodies of certain mollus- 

 cous animals, which may be imparted to the air 

 resting upon the surface of the water ; and Dumas, 

 in his report upon Lewy's Memoir, throws out some 

 remarks on the possibility of the sulphur contained 

 in this gas serving an important purpose in the 

 nutrition of plants. 



Y 4 



