EFFECTS OF VITIATED AIR 279 



a time, after which the cycle is repeated. This phenomenon appears to be 

 due to the want of action of some of the usual cerebral influences which pass 

 to and regulate the discharges of the respiratory center. 



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, uneasy sensations occur, such as headache, languor, and 

 a sense of oppression. It is a remarkable fact, however, that the organism 

 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, hos- 

 pitals, 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. 



