304 RESPIRATION 



Effects of Vitiated Air. Ventilation. As the air expired from the 

 lungs contains a large proportion of carbon dioxide and a minute amount 

 of organic matter, it is obvious that if the same air be breathed again and 

 again, the proportion of carbon dioxide and organic matter in it will con- 

 stantly increase till it becomes unfit to breathe; long before this point is 

 reached, however, sensations of uneasiness occur, such as headache, languor, 

 and a sense of oppression. It is a remarkable fact, however, that the organ- 

 ism after a time adapts itself to a very vitiated atmosphere, and that a person 

 soon comes to breathe, without sensible inconvenience, an atmosphere which, 

 when he first enters it, feels intolerable. Such an adaptation, however, can 

 take place only at the expense of a depression of all the vital functions, which 

 must be injurious if long-continued or often repeated. This power of adapta- 

 tion is well illustrated by an experiment of Claude Bernard. If a sparrow 

 is placed under a bell-glass of such size that it will live for three hours, be 

 taken out at the end of the second hour (when it could have survived another 

 hour), and a fresh healthy sparrow introduced, the latter will die at once. 



It must be evident that provision for a constant and plentiful supply of 

 fresh air, and the removal of that which is vitiated, are of greater importance 

 than the actual cubic space per person of occupants. Not less than 2,000 

 cubic feet per individual should be allowed in sleeping apartments (barracks, 

 hospitals, etc.), and with this allowance the air can be maintained at the 

 proper standard of purity only by such a system of ventilation as provides for 

 the supply of 1,500 to 2,000 cubic feet of fresh air per person per hour. 



Effects of Breathing Gases Other than the Atmosphere. Asphyxiation is 

 produced by the direct poisonous action of such gases as carbon monoxide, 

 which is contained to a considerable amount in common coal gas. The 

 fatal effects often produced by this gas (as accidents from burning charcoal 

 stoves in small, close rooms) are due to its entering into combinations with 

 the hemoglobin of the blood corpuscles and thus preventing the formation 

 of oxyhemoglobin because of the more stable carbon- monoxide hemoglobin. 

 The partial pressure of oxygen in the atmosphere may be considerably in- 

 creased without much effect in displacing the carbon monoxide, hence this 

 is rapidly fatal when breathed. Hydrogen may take the place of nitrogen 

 with no marked ill effect, if the oxygen is in the usual proportions. Sul- 

 phureted hydrogen destroys the hemoglobin of blood and thus produces oxygen 

 starvation. Nitrous oxide acts directly on the nervous system as a narcotic, 

 and may also form a compound with hemoglobin. Certain gases, such as 

 carbon dioxide in more than a certain proportion, sulphurous acid gases, am- 

 monia, and chlorine, produce spasmodic closure of the glottis and prevent 

 respiration. 



Alteration in the Atmospheric Pressure. Lower barometric pres- 

 sures than the normal occur in high altitudes, for example in mountain climb- 

 ing or in aerial navigation. The susceptibility to decrease in barometric 



