358 MANUAL OF PHYSIOLOGY. 



cubic space and a certain change of air for each individual, but 

 the cubic space and the change of air should bear to each other 

 a certain proportion in order that the air may remain sufficiently 

 pure. 



The space allowed in public institutions varies from 500 to 1500 

 cubic feet per head in such apartments as are occupied by the in- 

 dividuals 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, accompanied by a 

 series of phenomena, commonly included under the terra asphyxia, 

 which may be divided into four stages. 1. Dyspnoea. 2. Con- 

 vulsion. 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 mus- 

 cles 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. 



