DISEASES OF THE RESPIRATORY ORGANS. 



Importance of diseases of the respiratory organs — in horses and dogs. 

 Proclivity through over-exertion, through extent and delicacy of the mu- 

 cosa, through changes of temperature, through weather, through air pollu- 

 tion, through kind of diet, through change of latitude, through nervous 

 sympathy, through debilitation of the lung tissue, through suppression of 

 perspiration, through a high dew point, through bacteria and other germs, 

 through youth and change of habits. 



These are among the most freqvient and grave of all affections 

 of the domestic animals. They are especially important however 

 in the case of animals that depend on the soundness of their wind. 

 In horses and dogs accordingly anj^ permanent injury to the or- 

 gans of respiration will seriously impair the value, not only be- 

 cause of the diminished usefulness of the affected animal, but also 

 because of the probable deterioration of their progeny. The 

 rapid paces demanded of these animals and the strain to which 

 the respiratory organs are subject are potent causes of respiratory 

 disorder. In all animals, however, the extent of the respiratory 

 surface and its extreme delicacy and tenuity especially predis- 

 pose it to disease. Hales estimates that the mucous membrane 

 covering all the air sacs and air cells is, in the calf, no less 

 than 250 square feet. As the chest of the horse is at least 

 double that of the calf, and as it contains much less connective 

 tissue, and is made up of minute air cells from j^^ — -^^q inch in 

 diameter and separated from each other by walls so attenuated 

 that the contained capillary blood-vessels are equally exposed to 

 the air on both sides, in two adjacent air cells, the estimate for 

 the average horse must be considerably above 500 square feet. 

 This membrane, incomparably the most delicate and susceptible 

 in the animal economy, is constantly in contact with the air in all 

 its variable conditions, and is necessarily affected by these varia- 

 tions. 



The severe changes of temperature are not without their influ- 

 ence on this sensitive membrane. If these changes are sudden, 

 as for example in our northern states where the temperature will 

 var}' from 50° to 70° Fall., in a single day, the danger of injury 

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