362 MANUAL OF PHYSIOLOGY. 



The space allowed in public institutions varies from 500 to 

 1500 cubic feet per head in such apartments as are occupied by 

 the individuals day and night. As a fair average, 1000 cubic 

 feet may be fixed as the necessary space in a perfect hygienic 

 arrangement. In order to keep this perfectly wholesome and 

 free from a stuffy smell, and the CO 2 below .06 per cent., it is 

 necessary to supply some 2000 cubic feet of air per head per 

 hour. 



To give the necessary supply of fresh air without introducing 

 draughts or greatly reducing the temperature of the room is no 

 easy matter, and forms the special study of the hygienic engineer. 



ASPHYXIA. 



If the proper supply of oxygen be by any means withheld 

 from the blood so that its percentage is reduced to a certain 

 point, the death of the animal follows in 3 to 5 minutes, accom- 

 panied by a series of phenomena, commonly included under 

 the term asphyxia, which may be divided into four stages. 

 1. Dyspnoea. 2. Convulsion. 3. Exhaustion. 4. Inspiratory 

 spasm. 



If the air passages be closed completely, the respirations become 

 deep, labored and rapid. The respiratory efforts are more and 

 more energetic, and the various supplementary muscles are called 

 into play one after the other, until gradually the second stage is 

 reached in about one minute. 



As the struggle for air becomes more severe, the inspiratory 

 muscles lose their power, and the expiratory efforts become more 

 and more marked, until finally the entire body is thrown into a 

 general convulsion, in which the traces of a rhythm are hardly 

 apparent. This stage of convulsion is short, the expiratory 

 muscles becoming suddenly relaxed from exhaustion. 



Then the longest stage arrives in which the animal lies almost 

 motionless, making some quiet inspiratory attempts. These be- 

 come gradually deeper and slower, until they are nothing more 

 than deep gasps separated by long, irregular intervals. 



The pupils of the eyes become widely dilated, the pulse can 

 hardly be felt, and the animal lies apparently dead, when often 



