165 
ON GROUSE DISEASE, ETC. 
scribed. I will call the species by the provisional title of 
Strongylus pergracilis. Examples of this new species of 
parasite occupied the whole length of both of the intestinal 
caeca. They were present in greater or less abundance in 
all four of the birds. The male parasite gave an average of 
one third of an inch in length; the females extending up to 
three eighths of an inch, or rather more. The latter had 
their oviducts crowded with eggs arranged in single file, and 
displaying various stages of yolk segmentation; but I did not 
notice any fully formed embryos. It may afford some notion 
of the extraordinary abundance of these nematode entozoa, 
when I state that from less than a teaspoonful of the intes¬ 
tinal contents I obtained many hundreds of specimens. I 
am confident that no one of the four grouse contained less 
than a thousand examples, and I believe that one of the more 
diseased and emaciated birds contained fully ten times that 
number. 
That such a multitude of active nematodes could reside 
in the intestines of any bird without producing suffering or 
serious inconvenience to the bearer is hard to believe; and 
therefore, in the total absence of other evidence, it is perhaps 
not too much to assert that the murrain of the present season 
is attributable to the presence of multitudes of very fine 
strongles. I am perfectly well aware that birds can fly about 
with all sorts of strange entozoa in their bodies without ap¬ 
parently suffering in the least degree, and we have lately 
become acquainted with a singular instance of this apparent 
immunity. Professor Wyman found Eustrongyli surrounding 
the cerebellum of seventeen out of nineteen snake birds or 
water turkeys shot in Florida; and he remarks that the pre¬ 
sence of these threadworms c in the cranial cavity might be 
called the normal condition of this bird/ Dr. Wyman’s 
parasite is a viviparous form of nematode. (See f Proceed. 
Bost. Nat. Hist. Soc. 5 for 1868.) These and other like data 
do not, however, disprove the generally admitted conclusion, 
which I have over and over again had occasion to verify, 
that internal parasites are liable to occasion inconvenience, 
suffering, disease, and not unfrequently death itself, to their 
bearers, more particularly when they occur in excessive 
numbers. A parasite-bearer, like any given territory, can 
only support a certain number of occupants. In the case of 
entozoa an unusually wet season following a mild winter is 
eminently favorable to the excessive multiplication of certain 
forms of these creatures. 
“ Since dissecting the four grouse above referred to, I 
had an opportunity of examining with still greater care the 
