Medical Officers of the Army of India.
35
The scanty literature I possessed contained no reference to it, and I was
just going to write to my long-suffering friends at the Indian Museum, to beg
them to search out for me any references there might be to new ovine nematodes
that might have been described, with the view of describing it under the name
of S. orientate, should it prove to be new, when I met with, in the current
" Journal of the Royal Microscopical Society," a notice of a work by Dr. Curtice,
of Washington, United States of America, monographing the animal parasites of
sheep, and determined to hold my hand till I could obtain a copy. The work
is published by the United States Bureau of Agriculture, and I had some diffi-
culty in getting one. It is as well, however, that I delayed, as I found my
worm described in it as a new species, which would have had a priority of several
months to any description I might have published.
Nodular disease of the intestine had been, it seems, known as a widely-spread
and fatal disease among sheep in America for many years, but investigators had
wasted their energies in fruitless searches for the tubercle bacillus ; and it was
reserved for Dr. Curtice to demonstrate the true cause of the disease, an
achievement which he looks upon as the most important outcome of a long and
exhaustive investigation into the ovine helminthology of North America.
His descriptions and observations generally coincide exactly with my own in
every particular, except that he is unaware of the existence of a free stage to the
worm, and assumes that sheep are directly infected by swallowing the ova. My
measurements of the ova give a somewhat smaller figure than his ; but I notice
that this is the case also with the ova of other parasites which we have both
measured; so that it is probably due, not to any difference in the material observed',
but to some error in the methods employed by one or the other of us. My own
measurements were taken by comparing the size of a camera lucida drawing of
the ova with that of a micrometer scale, the two drawings being made under abso-
lutely unchanged conditions, the micrometer being merely substituted for the
slide, and its divisions drawn beside the outline of the preparations. The ac-
curacy of the micrometer employed was also tested by comparing a drawing of it
under a low power with those of an actual full-sized engineer's scale ; so that I
see little room for error in my determination, and am inclined to prefer them to
those of Dr. Curtice, who may have employed merely the eye-piece micrometer,
an instrument which is apt to give only approximate results, small differences in
the focussing of the eye-piece scale leading to perceptibly discrepant results.
The description below is taken from Curtice, but with some minor additions.
Œsophagostom columbianum, Curtice.—Description. —Male, 12 to 15 mm. long ;
female 14-18 mm. (Curtice.) (I have a female specimen measuring 22.86 mm. or
0.9 " ). Body, of nearly uniform diameter throughout, tapering abruptly at
head and tail. Greatest diameter, in both sexes, about middle of body-length ;
1 United States Department of Agriculture, Bureau of Animal Industry : —" The Animal Parasites
of Sheep," by Cooper Curtice, P.V.S., M.D.—Washington, Government Printing Office, 1890.
F2