178 Life and Health 



267. The Object of Ventilation. The question of a prac- 

 ticable and economical system of ventilation for our homes, 

 schoolrooms, workshops, and public places presents many 

 difficult and perplexing problems. It is perhaps due to the 

 complex nature of the subject that ventilation, as an ordi- 

 nary condition of daily health, has been so much neglected. 

 The matter is practically ignored in building ordinary houses. 

 The continuous renewal of air receives little, if any, consid- 

 eration, compared with the provision made to furnish our 

 homes with heat, light, and water. 



The object of ventilation should be twofold : first, to 

 provide for the removal of the impure air ; second } to provide 

 for a supply of pure air without cold draughts. This is one of 

 the most difficult of sanitary problems. 



ANIMAL HEAT 



v 



268. Animal or Vital Heat. If a thermometer, made for 

 the purpose, be placed for five minutes in the armpit . or 

 under the tongue, it will indicate a temperature of about 

 98^- Fahr., whether the surrounding atmosphere be warm 

 or cold. This is the normal temperature of a person in 

 health, and it rarely varies more than a degree or two. 

 Now, as the body is constantly losing heat by radiation and 

 conduction, it is evident that if the normal temperature 

 be maintained, a certain amount of heat must be generated 

 within the body to make up for this 'loss. 



The heat thus produced is known as animal or vital heat. 



269. Sources of Bodily Heat. The heat of the body is 

 generated by the chemical changes which are constantly 

 going on in the tissues. These chemical changes are of 

 various kinds, but the great source of heat is the katabolic 

 process known as oxidation. 



