Ventilation of Farm Buildings. 353 



It should be cleaily recognized that the germs of diph- 

 theria, of tuberculosis, hog cholera and other contagious 

 diseases are liable to be met with almost any day and in 

 any place and that wherever a proper breeding place may 

 be found the disease is liable to start and from, it spread by 

 force of greater numbers of germs. 



While therefore the micro-organisms usually found in 

 greatest numbers in dusty houses and stables poorly venti- 

 lated and cared for are not in themselves a source of dan- 

 ger, the run-down, weakened condition which poor ventila- 

 tion is sure to engender will certainly tend to start a case 

 of contagious disease and then, with greater numbers of 

 germs in the air to be introduced into the system, animals 

 of greater vigor must succumb to these invisible foes be- 

 cause of their vast numbers. 



Ample ventilation then should always be secured, first, 

 as an indispensible condition for maintaining the power 

 to resist disease, and second, in case of disease, to both clear 

 the air and to give the animals an opportunity to defend 

 themselves against this type of foe. 



437. Amount of Air Respired. The amount of air ordi- 

 narily taken into and put out of the lungs by man with 

 each respiration is given by different observers as follows: 



Herbst 20 30 cubic inches 



Valentin 14 92 cubic inches 



Vierordt 10 42 cubic inches 



Coathupe 16 cubic inches 



Ilutchinson . 16 20 cubic inches 



Average 15.2 46 cubic inches 



or an average of about 30 cubic inches. 



The amount of pure air which must be breathed in order 

 to supply the oxygen needed by different animals, deduced 

 from Colin's table, is given below: 



