AND LECTURES. 39 
ofan animal. Sometimes many of these small air cells are 
ruptured, larger ones being thus formed by reason of the 
fact that they break into each other. When this happens 
that port:on of the lung involved loses largely its power of 
involuntary contraction; in this event the diaphragm, ribs 
and abdominal muscles are brought into play in expelling 
_air from the lungs, the exercise of these giving rise to the 
twitching seen in the flanks. 
Cause—It is sometimes produced by driving rapidly in 
the face of heavy wind, particularly when the horse is not 
| in condition to stand it, and it may be brought on by 
_ exercising too freely when the stomach of the animal is too 
full of bulky food to allow free expansion of the lungs. 
| Again it may be caused by too violent exercise when the 
lungs are weak from cold, a severe spell of sickness or 
| where the horse has been fed on dusty or smutty food. 
HOW TO KNOW Nghe 
_ There will be a deep cough, and instead of the regular, 
easy breathing there will be a twitching of the muscles of 
the flanks or a kind of secondary effort upon their part at 
every respiratory act. The nostrils will be distended, and 
by ausculation we observe a popping, crushing sound. 
When this sound is heard we can not be mistaken, for it is 
present in no other disease An animal thus affected will 
have no food, the pulse will run a little above normal, how- 
ever. If you are buying or trading for a horse that you 
have any reason to suspicion is one that the heaves have 
been ‘‘shut down’’ upon, (as the jockeys call it) I would 
advise that you examine his lungs and under no circum- 
