RESPIRATION (Germ. Athnzung).—Be fore the nutritious juices of organized bodies can be properly elaborated and rendered fit for maintaining the vitality of the tissues through which they move, it is indispensable that certain chemical changes take place between them and the atmospheric air. All organized bodies, therefore, vegetable as well as animal, require a supply of atmospheric air for the continuance of life, and the amount of this is proportionate to the number and energy of their vital actions. These chemiCal changes between the nutritious juices of organized bodies and the atmospheric air constitute the important function of Respiration.
In studying the chemical actions that occur in respiration in different organized bodies, it is necessary to keep in mind the constitution of the atmospheric air, both in its free state and when dissolved in water. The atom. spheric air, in its free state, is, as is well known, chiefly composed of nitrogen and oxy gen, in the proportion of about 21 parts of oxygen to 79 of nitrogen by volume ; or by weight, in the proportion of 23.1 of oxygen to 76.9 of nitrogen. Dumas and Boussingault, in their accurate experiments*, found the average proportion of these gases to be, by volume, 20.81 of oxygen, and 79.19 of nitro gen ; or by weight, 23.01 or oxygen, and 76.99 of nitrogen. The quantity of carbonic acid gas in the atmospheric air is very much smaller than that of the oxygen and nitrogen. Theod. De Saussure $, in his experiments, 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 Thenard t at Paris, Brunner t 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 11 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 I and Morrell**, the composition of the air near the surface of the sea differed in its amount of oxygen froni that over the land. Saussure detected a somewhat smaller quan tity of carbonic acid gas in the air during the day 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. t Lewy detected a considerable increase of carbonic acid gas, no doubt of volcanic origin, in the air of Guadaloupe, but without any diminution in the usual relative proportions of the oxygen and nitrogen.$ 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. 11 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.cif 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 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.