170 RESPIRATION". 



formation of oxygen into carbonic acid in the blood, in treating of the different methods 

 of analysis of the blood for gases, and have shown that this gas is the proper agent to 

 use in the method of analysis by displacement. 



In breathing in a confined space, the distress and the fatal results are produced, in 

 all probability, more by animal emanations and a deficiency of oxygen than by the pres- 

 ence of carbonic acid. When the latter gas is removed as fast as it is produced, the effects 

 of diminution in the proportion of oxygen are soon very marked, and they progressive- 

 ly increase until death occurs. Bernard has shown that birds enclosed in a confined space, 

 from which the carbonic acid is carefully removed, will gradually consume oxygen, un- 

 til, when death occurs, the proportion is reduced to from three to five parts per hun- 

 dred. When the carbonic acid is allowed to remain, the increased density of the atmos- 

 phere interferes with the diffusion between the gases of the blood and the air, and death 

 supervenes with greater rapidity. 



The influence on animals of emanations from the lungs and general surface is un- 

 doubtedly very considerable ; and this fact, which almost all have experienced more or 

 less, has been fully and painfully illustrated in several instances of large numbers of per- 

 sons confined without proper change of air. Overcrowding is one of the most prolific 

 sources of disease among the poorer classes of society ; and there are many forms of dis- 

 ease prevalent in large cities, that are almost unknown in the rural districts and that can 

 be alleviated only by proper sanitary regulations, which, unfortunately, are often very 

 difficult to enforce. 



In crowded assemblages, the slight diminution of oxygen, the elevation of temperature, 

 increase in moisture, and particularly the presence of organic emanations, combine to 

 produce unpleasant sensations. The terrible effects of this carried to an extreme degree 

 were exemplified in the confinement of the one hundred and forty-six English prisoners, 

 for eight hours only, in the "Black Hole" of Calcutta, a chamber eighteen feet square, 

 with only two small windows, and those obstructed by a veranda. Out of this number, 

 ninety-six died in six hours, and one hundred-and twenty-three, at the end of the eight 

 hours. Many of those who immediately survived died afterward of putrid fever. This 

 frightful tragedy has frequently been repeated on emigrant and slave ships, by confining 

 great numbers in the hold of the vessel, where they were entirely shut out from the 

 fresh air. This subject possesses great pathological interest ; the effects of an insufficient 

 supply of air and the accumulation in the atmosphere of animal emanations being very 

 important in connection with the cause and prevention of many diseases. 



The condition of the system has a marked and important influence on the rapidity 

 with which the effects of vitiated atmosphere are manifested, as we should anticipate 

 from what we know of the variations in the consumption of oxygen under different con- 

 ditions. As a rule, the immediate effects of confined air are not so rapidly manifested in 

 weak and debilitated persons as in those who are active and powerful. It has sometimes 

 been observed, in cases where a male and female have attempted suicide together by the 

 fumes of charcoal, that the female may be restored some time after life is extinct in the 

 male. This is probably owing to the greater demand for oxygen on the part of the male. 



The following interesting fact is reported by Bernard, showing the relative power of 

 resisting asphyxia in health and disease : 



" Two young persons were in a chamber warmed by a stove fed with coke. One of 

 them was seized with asphyxia and fell unconscious. The other, at that time suffering 

 with typhoid fever and confined to the bed, resisted sufficiently to be able to call for help. 

 We know already that this resistance to toxic influences is manifested in animals, when 

 they are made sick ; we here have the proof of the same phenomenon in man. As for tlie 

 one who, in good health, had experienced the effects of the commencement of poisoning, 

 she had a paralysis of the left arm, which was not completely cured at the end of six 

 months." 



When poisoning by confined air is gradual, the system becomes somewhat accustomed 



