34 The Management and Diseases of the Dog. 
bryos were inhaled with the breath, and, lighting ia 
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 airrather 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 
pronchial 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 
