Diseases of the Respiratory Organs. 73 



becomes immineut, and the lungs require to be strong indeed to 

 resist their effects. Sudden transition from the hot close atmos- 

 phere of the barn or stable to the chilling winds of winter is 

 equally hurtful. But it is not alone the transition from warmth 

 to cold that is injurious. The general relaxation attendant on 

 the sudden change from a cold bracing atmosphere to one unduly 

 hot is even more injurious. How frequently do human beings 

 suffer from colds as the result of a close sultry period at once su- 

 pervening on a clear cold one ? How extensively do chest dis- 

 eases prevail among horses brought from the clear pure atmos- 

 phere of the field, and shut up in close, hot stables ? Here, no 

 doubt, there is superadded the impurity of the too often infected 

 air, the change of diet, of exercise and of general care j'et we 

 find that affections of the air passages are to a great extent in 

 ratio with the heat of the building. Hence their constant pres- 

 ence in dealer's stables where it is thought desirable -to keep the 

 horses warm to hasten the improvement in the coat. 



The suddenness of the transition is usually a principal cause of 

 injury. Where the climate changes slowly the animal economy 

 becomes habituated to it and resists successfully the injurious in- 

 fluences. Thus when spring merges gradually into summer and 

 autumn into winter, diseases of this kind are far less frequent. 

 But on the other hand a sudden and extreme variation of tem- 

 perature, whether in the ordinary course of the season or from a 

 wide change of latitude, is notoriously attended with diseases of 

 the air passages. Ayrshire, shorthorn and Jersey cattle, when 

 first imported into the Northern States of America, contract colds, 

 consumption and other chest diseases to a far greater extent than 

 the native races, though their progeny or even they themselves 

 after acclimatization, exhibit powers of resistance nearly equal to 

 the native stock. Sheep that have been shorn in midwinter or 

 early spring often repay the inhumanity of their owners by dying 

 of inflamed lungs. Southdown and I^eicester sheep, sent from 

 England to the north of Scotland, demand at first the greatest 

 care to protect them against the increased rigor of the climate. 

 The army veterinary statistics of France show that horses trans- 

 ported from the southern parts of the country to the more northern 

 stations, suffer largely from pulmonary affections. But if the 

 change is effected slowly the requisite powers of resistance are 



