BRONCHITIS. 121 



the cause of tliis disease, for tliere are often cases occur where it 

 caanot be due to cold or exposure, especially in the spring and fall 

 months, and it is sometimes seen where a number of puppies are 

 housed together, or in some cases attacking older dogs. In some 

 of these outbreaks it is quite difficult to distinguish it from dis- 

 temper. (See Infectious Bronchial Catarrh.) 



Pathological Anatomy. In describing any catarrh of the 

 trachea it should be classed under the head of bronchitis, as it is 

 impossible to draw the line of distinction between the two. In 

 bronchitis the mucous membrane is diffused, red, swollen, and 

 tears easily to the touch. la the earlier stages of the disease there 

 is little mucus found on it, but as the disease goes on to the later 

 stages the secretion becomes more copious and turbid or yellow 

 with pus-corpuscles; later on it becomes more or less colored with 

 blood- corpuscles. 



Chronic Catarrh. In this condition the color of the mucous 

 membrane is brownish-red or violet and the membrane is fre- 

 quently uneven and thickened; the secretion is clammy, slimy, or 

 shining, in some cases bad-smelling or even putrid. 



In old chronic cases of bronchitis there may be some stenosis 

 of the tubes, and also, from the constant irritation of the bronchia, 

 emphysema of the lungs. 



Stenosis (contraction) of the bronchia may be caused either by 

 swelling of the bronchial mucous membrane or by the collection 

 of masses of thickened secretion in the tube. In some cases the 

 two causes acting together exclude the air from the alveoli of that 

 part of the lungs to which the affected bronchia carry the air, 

 causing the lung-tissue to collapse. This condition, which origi- 

 nates in the manner described, does not change in its structure, 

 but soon becomes solidly filled with blood. 



In all chronic conditions we also find the opposite of stenosis — 

 that is, Bronchiectasis (widening of the bronchial tubes); this is 

 caused by a relaxed condition of the bronchial walls, due to the 

 chronic irritation and also to the pressure of collections of the 

 secretions. This dilatation of the tubes may be either cylindrical 

 or spindle-shaped. 



Emphysema of the Lungs. This is found near the atelectasic 

 centres and on the borders of the lungs; this condition is supposed 

 to be caused by violent coughing spells and also by bronchitis. 



