DISEASES OF RESPIRATORY PASSAGES AND ORGANS. $9 
‘twelve per minute, varying, however, according to the tempera- 
ment of the animal and the condition he may be in at the time 
of making the observation; while in horses the respirations are 
more frequent, varying in health, and when at rest, from fourteen 
to twenty-five; yet, under excitement and disease, they sometin:ea 
aumber over one hundred. 
THE CONTENTS OF THE THORAX. 
@upLaKation.—Fig. 1, Trache ; 2, Bifurcation of the carotid artery; 8, Internal carotid artery 
4 4, Anterior lobes of the lungs; 5 5 Posterior lobes of the lungs; 6, The heart; 7, Ooronw 
actery; 8 Cartilages of the false ribs; 9, The diaphragm. 
When an animal is located in a pure atmosphere, and th- 
lungs are in good working condition, all the impurities containe | 
in venous blood are brought into the presence of oxygen throug! 
the lining membrane of the air-cells, and thus a change in th 
color and character of the blood is immediately effected. In thi 
first place, the venous blood, as it appeared before having beet 
submitted to the action of the atmosphere, was of a dark purpl: 
