AND HIS DISEASES. 135 



CONGESTION OF THE LUNGS. 



Before proceeding to consider the diseases of the chest, we 

 will briefly notice the structures involved in pulmonary affec- 

 tions. The windpipe (trachea), after entering the chest, 

 divides into the bronchia or bronchial tubes. These divide 

 and subdivide into smaller tubes, finally terminating in the air 

 cells. The lungs are made up of clusters of those cells; of a 

 large mass of pulmonary texture called the parenchymatous 

 structure or substance of the lungs' ; of blood-vessels, both 

 functional and for the nutrition of the organ ; of nerves and 

 lymphatics, and the whole enclosed in a serdus membrane 

 called the pleura, which is made up of two portions — one 

 portion being reflected over the lungs (pleura pulmonalis), 

 while the other lines the inside of the ribs and diaphragm 

 (pleura costalis). The lungs are exceedingly light in propor- 

 tion to their size, and are very vascular organs ; consequently 

 we find them very liable to diseases of an inflammatory cha- 

 racter, and the precursor of inflammation is congestion. 



Congestion of the luiigs, a disease common amongst our 

 Canadian horses, consists in an increased determination of 

 blood to the capillaries of the air cells, interfering materially 

 with the process of respiration. It may exist as an inde- 

 pendent disease, or accompany other affections of the chest. 



Causes. — Perhaps one of the most common causes is vio- 

 lent .exertion when an animal is in an unfit state for severe 

 work — as, for instance, a young horse in, high condition is 

 taken out of his stable and driven rapidly for five or six 

 mQes ; this causes an increased quaptity of blood to the 

 lungs more than those organs are able to dispose of in their 

 weakened condition from the want of regular exetcise. It is 

 also caused by impure air, in horses standing in crowded 

 stables, and it is often a sequel of catarrh, 



