12 



ANIMAL MANAGEMENT. 



oxygen passing into the blood corpuscles, and carbonic acid gas into the 

 lung. Recharged with oxygen, and its vivid scarlet colour restored, 

 the blood is again fit for use, and returns to the heart, while the next 

 expiration discharges the used air from the lung. 



This revivification of the blood by the passage of oxygen into the red 

 corpus9les, and of carbonic acid out of them, is a necessary of life ; without 



it the blood becomes dark red, purple, and black successively as this 

 want is felt, and if not supplied, suffocation takes place. 



This constant demand for the supply of fresh air makes the necessity 



for free ventilation apparent. 



The The changes of position which actually take place between the various 



changes of organs during breathing are important when viewed in their relation to 



position, feeding and work (Fig. 2). When the breath is drawn into the lungs 



