144 DISEASE IN WILD MAMMALS AND BIRDS 
To what extent do the parasites predispose to pneu- 
monia? Compare for this purpose the two columns of 
Table 8 showing active and inactive pulmonary parasi- 
tism. In Rodentia and Galli alone do we note that active 
parasitism is eifective, there being no passive cases. In 
all the other orders, animal invaders of the lung are more 
often encountered as quiescent or encapsulated bodies, 
therefore as findings incidental to the autopsy and per- 
haps not concerned in the cause of death. In Ungulata 
the inactive parasitisms are five times as frequent as the 
active inflammatory lesions. It might be added that the 
list is made up of cases wherein we saw parasites whether 
determdned or not, an explanation of the apparently small 
number of cases; there were many more in which such 
invaders were suspected but not found and there- 
fore excluded. 
Bronchiectasis. 
Bronchiectasis affecting the smallest tubes, or bron- 
chiolectasis, is not at all uncommon in verminous pneu- 
monitis and is explained as due to the degeneration of the 
wall, the surrounding progressive ulceration, to accumu- 
lation of inspired air and its retention by the obstruction. 
There is described a generalized broncliiolectasis, chiefly 
in young human beings, due to a destructive bronchio- 
litis ; this has not been seen. 
Non-verminous bronchiectasis of the middle sized 
bronchi such as is seen in human chronic bronchitis, 
simple or tuberculous, is quite uncommon. Widening of 
the bronchial lumen may be di\dded, as I see its path- 
ogenesis, into (a) that due to congenital weakness of the 
walls, (b) that due to obstruction permitting air to pass 
into but not out of a bronchus because of a ball-valve 
obstruction or weakness of expiratory power, (c) that due 
to external pressure by tumors or distortion by fibrous 
tissue either within the lung or pleura and (d) that due to 
inflammatory weakening of walls, augmented by loss of 
