618 DISEASE IN WILD MAMMALS AND BIRDS 
narrow gut and comparatively large parasite induced 
obstruction. Plimmer(3) records microfilaria clogging 
the brain capillaries. Shipley (4) mentions two specimens 
of Ascaris liimhricoides obstructing the nares of a chim- 
panzee {Pan niger). Blockage may also be produced sec- 
ondarily to the presence of the parasite, even in the 
absence of notable numbers of them, and quite apart from 
the element of verminous bulk. This occurs through in- 
flammatory swellings which the worms excite. We saw 
mmiy serious grades of this in our spiroptera epizootic, 
the lumen of the proventricle being narrowed by swelling 
of the mucosa and more or less occluded by exudate and 
necrotic mucous membrane. 
Yet another direction wherein a mechanical rationale 
pure and simple obtains is by the production of divertic- 
ula. Worms encysted in the gut wall may, by weight 
alone or by excitation of peristalsis, cause the wall to 
bulge outwards (or inwards even) like a pocket. Such a 
diverticulum has been noted in the gut of a Pale Cebus 
{Cehus flavescens) (5) parasitized by acanthocephalus, 
but in this case there were adhesions to the nearby 
stomach, and it is possible that in this individual case the 
diverticulum was a traction one, i.e., pulled out by the 
anchorage of adhesions externally. 
2. Mechanical Irritation. — In those instances where 
inflammation is the manifestation which reflects the 
simple mechanical effects of parasites it vdW be difficult 
indeed to prove, in the present state of our knowledge, 
that it is not rather the effect of associated toxic sub- 
stances or excreta elaborated by the parasite. But 
instances of a purely mechanical irritation there must 
be, although one can scarcely put the finger upon them 
and say that this or that individual inflamed mucosa did 
not become so from a toxic cause. Omitting these then, 
(3) Proc. Zool. Soc. London, 1910, p. 134. 
(4) Proc. Zool. Soc. London, 1905, p. 252. 
(5) Phila. Zool. Soc. Rep., 1920, p. 29. 
