The Breathing Organs, J 9 



The nerves respond to the diseased condition of the brain 

 either by excessive and violent action, as displayed in the 

 spasms of megrims, epilepsy, lockjaw and hydrophobia ; or 

 else by a more or less complete loss of their power of convey- 

 ing sensation and motion, as in the varieties of palsy. 



What physicians call " diseases of the mind,'^ as insanity 

 and idiocy, do not seem to occur in the lower animals; 

 although instances are recorded where horses have apparently 

 deliberately committed suicide, which w^ould appear to be an 

 evidence of hypochondria. 



THE ORGANS OF BREATHING. 



These consist of the lungs, and the tubes through which 

 Air is conducted into them. The lungs are composed of 

 millions of little sacs or vesicles, each vesicle opening into 

 a minute tube, which tubes unite to form others of larger 

 calibre, called bronchi; and finally all the bronchi join the 

 lower end of the windpipe or trachea, which continues up 

 the throat to the mouth. The lungs do not lie immediately 

 against the walls of the chest, but against a close msmbra- 

 nous sac called the pleura, which lies between the lungs and 

 the ribs. 



The act of breathing differs in frequency in different ani- 

 mals. In the horse it averages in health ten or twelve times 

 a minute, in the ox twelve or fourteen times, in man sixteen or 

 eighteen times. It should also be quiet and regular, and any 

 deviation from these natural conditions is justly regarded 

 with suspicion. A warranted horse is held to be especially 

 guaranteed " in wind and limb," any defect of the breathing 

 organs being mentioned first as of first importance. 



When the minute vesicles of the lungs are inflamed we 

 have the disease called inflammation of the lungs, lung fever 

 or pneumonia; when the inflammation is in the tubes or 



