CAUSES OF PULMONARY DISEASE. 73 



horses on becoming domiciled are incomparably more subject 

 to it than such as are aged and seasoned. And horses that 

 are high-bred and tenderly reared, and have light carcases, 

 long legs, flat sides, and breasts so narrow that both fore-legs 

 seem as though they " emerged from one hole," and who 

 possess thin skins, are indisputably more susceptible than 

 those of a difi'erent breed and opposite conformation. 



The CAUSES OF pulmonary disease will, in a general 

 way, be found in the air horses breathe and in the work 

 they perform; in fact, they may be said to date their pro- 

 bable rise from the day the animal is taken into the stable 

 and made the servant of man — in one word, from his period 

 of domestication. 



The AIR the horse is compelled to breathe while confined 

 in his stable may be cold or heated, moist or dry, pure or 

 impure, considered in relation to the atmosphere out of 

 doors. There can be no doubt that either excess of tempe- 

 rature — cold or heat — must have an excitant operation on 

 the membrane lining the respiratory passages; and yet it is 

 a notorious fact, that horses usually enjoy vigorous health 

 in frosty weather. Cold with damp, however, has certainly 

 an unfavorable operation. Wet springs and autumns are 

 commonly productive of a good deal of sickness. Is this to 

 be ascribed to any direct efPect upon the air-passages, or is 

 it to be attributed to some operation upon the skin ? — and 

 particularly since these are the moulting seasons? In the 

 latter case, the lungs become secondarily or sympathetically 

 affected. Even here, however, we appear to require the 

 presence of some stimulant — such as heat or foul air- — 

 before disease will show itself; for horses out in the open air 

 during such insalubrious seasons, rarely, if they do at all, 

 contract the prevailing malady. In a general way, and in 

 regard to its direct operation upon the bronchial membrane, 

 cold must be regarded as a predisponent to disease; and not so 

 much cold by itself, as cold with humidity, or even a particu- 

 larly drying cold : the probability being, that the effects are 

 not owing simply to any sedative operation the cold may have 

 on the membrane, but also to the operation it has upon it as 



