34 The Management and Diseases of the Dog. 



bryos were inhaled with the breath, and, lighting in 

 the mucous membrane, found suitable conditions for 

 development. The position of the parasites about the bi- 

 furcation of the trachea, at the angles of division of the 

 main bronchi, and most abundantly in the lower 

 wall of the tubes, just the localities where small 

 particles would be most likely to lodge, favours an infection 

 through the air rather than by the blood. The negative 

 evidences in the heart and blood-vessels do not go for much 

 ■either way, as the examination in all the cases was made 

 after the invasion of the parasites, and consequently at a 

 time when they could scarcely be found in the circulation. 

 " It is a somewhat remarkable fact that verminous bron- 

 chitis prevails to a much greater extent and is more fatal 

 in young animals than in adults. Thus lambs and calves 

 are the chief victims in epidemics of ' hoose,' whereas it is 

 only occasionally that adult animals succumb to the 

 disease. In lambs the worms are usually found in the 

 bronchial tubes, while in sheep they are more commonly 

 encysted in the lung-tissue itself where they do not appear 

 to cause much irritation. It seems to me that in the ana- 

 tomical peculiarities of the lungs in young animals we have 

 an explanation of the fatality of the disease among them. 

 If the bronchial tubes of a young animal be compared with 

 those of an adult, they are seen to be softer, much less rigid ; 

 the mucous membrane is lower, not so thin, nor so closely 

 attached to the tissues beneath. Hence it happens that in 

 inflammation of the tubes from any cause, swelling and 

 tumefaction of the mucous membrane readily occur, and 

 constitute elements of danger which are directly propor- 

 tionate to the calibre of the tubes attacked. In the cases 

 above reported the swelling of the membrane in the larger 

 tubes was considerable, and, though not sufficient to prevent 

 the access of air, must have interfered greatly with the ex- 

 pulsion of mucus from the smaller tubes, not only by 

 decreasing and narrowing the orifices of exit, but also by 



