ASPHYXIA IN A LIMITED QUANTITY OF AIR. 743 



differ in different individuals. In one case the hyperpnoea became 

 appreciable at about 12 per cent., and excessive at about 6 per cent." 



These observers also point out that the odorous substances arising 

 from want of cleanliness of the body or the room, are also causes of the 

 discomfort experienced in breathing the air of an overcrowded room. 



The causes of asphyxia in a limited quantity of air. A 

 warm-blooded animal confined in a limited quantity of air soon gives 

 signs of discomfort ; it becomes restless, breathes more rapidly, and 

 soon pants for breath. This stage is succeeded by one during which 

 the animal is quieter, breathes more slowly but more deeply ; it becomes 

 less sensitive, and falls down ; agonising efforts are made to breathe, the 

 nostrils are dilated, and the mouth is open. The animal now becomes 

 unconscious, its pupils are dilated, it gives a few slight and irregular 

 respirations, it is seized by convulsions, and then, after a slight pause, its 

 limbs are stretched out with a convulsive shivering movement, its head 

 is thrown back, and it dies. 



The general phenomena of asphyxia are described elsewhere in this 

 work ; l here it is necessary to consider only the chemical changes in the 

 air, the alterations they produce in the respiratory exchange of the 

 animal, and how they cause its death. Upon these questions numerous 

 experiments have been made. 2 



The duration of life in a limited quantity of air depends upon 

 various conditions, such as the amount and temperature of the air, the 

 nature and age of the animal. The following table of some of Paul 

 Bert's experiments will illustrate the influence of some of the above con- 

 ditions, and will show the composition of the air at the time of death : 



1 Article " Mechanism of Respiration," this Text-book, vol. ii. 



2 Edwards, " De 1'influence des agens physiques sur la vie," Paris, 1824; Collard de 



