EFFECTS OF BREATHING IMPURE AIR. 857 



cular system generally, but they do not restore the circulation through 

 the lungs. The injection of vapor, and of hot water at the tempera- 

 ture of 120, into the veins, excites the action of the heart in an extra- 

 ordinary manner; whilst that of warm defibrinated and deoxygenated 

 blood has no effect. Galvanism, applied to the heart jointly with arti- 

 ficial respiration, excites both sides of that organ, and, for a time, re- 

 stores the pulmonary circulation. The forcible injection of blood into 

 the jugular vein, with the view of overcoming the resistance to the 

 motion of the blood in the lungs, entirely fails in its object. On the 

 other hand, suction of the blood, by aid of a syringe introduced into a 

 large artery, draws some of that fluid through the pulmonary capillaries, 

 in an oxygenated state, and on its being reinjected into the artery, so 

 as to reach, amongst other parts, the walls of the heart through the 

 coronary arteries, effectually re-establishes the pulmonary circulation 

 and all the functions of the body. The injection of the blood back 

 into the artery, in a pulsatory or interrupted manner, revives the action 

 of the heart most completely from its quiescent, cold, and partly rigid 

 state, even one hour and jive minutes after death. These interesting 

 experiments, though not yet of practical application in the treatment 

 of asphyxiated persons, serve to corroborate the generally-received 

 opinion, that an essential fact in asphyxia, is the retardation, and sub- 

 sequent arrest, of the movement of the blood through the pulmonary 

 capillaries, and point to the reliefer removal of that condition, as the 

 turning-point of success in all attempts at resuscitation. 



Effects of Breathing Impure Air. 



Instances have occurred, in which the carbonic acid exhaled by large 

 numbers of persons crowded together in small apartments has been 

 most destructive to human life. The Black Hole of Calcutta was a 

 room only 18 feet square, having two small windows; into this apart- 

 ment, 146 prisoners were literally crammed, and, during one night, 

 123 of them perished. The cruelty of an enemy, in 1756, was scarcely 

 more disastrous than the ignorance of the captain of an Irish passenger 

 steamer, in 1848, who, during a storm, confined under closed hatches 

 in a small crowded cabin, 150 passengers, of whom 70 died in the night. 



But carbonic acid produces injurious effects, even when it exists, in 

 the air, in quantities too small to cause asphyxia ; as, for example, 

 when not more than one per cent, is present. Thus, in ill-ventilated 

 apartments, the presence of an excess of carbonic acid in the atmos- 

 phere, interferes with the proper oxygenation of the blood; for, as 

 already mentioned, less and less carbonic acid is exhaled, as the pro- 

 portion of that gas increases in the inspired air. Headache, oppres- 

 sion of the senses, lassitude of the muscles, and languor of the mind, 

 are the results; the oxidation of the effete matters of the blood, is im- 

 perfectly performed or prevented, and they accordingly accumulate in 

 that fluid ; the pulmonary and cutaneous exhalations become still more 

 loaded with such substances, and, together with the carbonic acid itself, 

 and the ordinary exhalations from the skin and lungs with which the 

 air in such confined apartments is already infected produce still more 



