Notes on 
Parasites. 
f, MYZOMIMUS. 
BV 
CHARLES W. STILES, Ph. D., 
Washington, D. C. 
The Journal of Comparative Medicine 
and 
Veterinary Archives, 
Reprint front 
February, 1892. NOTES ON PARASITES.* 
Charles W. Stiles, Ph. D 
In 1869 Prof. Mueller, of Vienna, found a curious threadworm 
in the oesophagi of five or six Polish and Hungarian cattle and in 
the oesophagus of an old horse, and described the same as Spirop- 
tera scutata oesophagea bovis, giving at the time a short diagnosis of 
the animal in Latin. The same parasite is reported by Harms and 
Ziirn from the oesophagi of sheep, and by Korzil from swine. 
All of these observations were made in Europe, and the various 
authors have added scarcely anything to the data given by 
Mueller. 
At Washington, D. C., this parasite is quite frequent, and has 
been observed by Dr. Curtice and Dr. Hassall as well as by myself. 
Upon studying the helminth, I have found several anatomical 
characteristics which scarcely agree with the description given in 
most text-books at present, and furthermore, I am convinced that 
the anatomical characters which are described below are sufficient 
to exclude the parasite in question from the genera Filaria and 
Spiroptera in which it is generally placed, so that I have, although 
somewhat reluctantly, created a new genus for it under the name 
Myzomimus. 
Myzomimus gen, nov. Stiles, 1892. Diagnosis Long filiform 
worms, of nearly uniform thickness throughout the entire length, 
except at the head and tail, where they are slightly attenuated. 
Type specimen (M. scutatus), inhabiting the epithelium of the 
oesophagus in cattle. Head slightly compressed laterally, tail 
♦Preliminary note on Myzomimus gen. Nov., type species M. scutatus, Mueller, ’69, a parasite 
in cattle. (male) compressed dorso-ventrally. Anterior portion of body beset 
for 1-3 mm., with shield-like differentiations of the cuticle, and 
with side membranes (wings or folds) ; mouth small, unarmed, 
oblong dorso-ventrally; lips absent; two minute oral papillae, 
placed laterally. In the median lines, directly back of mouth, are 
two semi-lunar sucker-like depressions, hence the name Myzomimus, 
from the Latinized Greek, meaning something which imitates or re- 
sembles a sucker. Two very large circular cervical papillae, cuticle 
finely annulated. (Esophagus divided into two portions Male 
smaller than female, with tail curved ventrally; six pairs of prae- 
anal papillae and 4-6 pairs of post-anal papillae ; lateral folds of 
tail asymmetrical; anus in front of tip of tail; right spicule short and 
stout; left spicule very long and slender; one testis present Female, 
vulva in posterior portion of the body; vagina long ; uterus double. 
Species Myzomimus scutatj/f, Mueller, 1869. The following may 
be added to the characters given above. The shields are arranged 
nearly symmetrically in the four sub-median fields ; generally a 
continuous or interrupted row of shields is found in each field, to- 
gether with other shield in various positions. Rings of the cuticle 
0.008 mm. broad. Side membranes do not extend far beyond the 
shielded portion, and are interrupted or broken in several places. 
Male 4-5 cm. long. (Esophagus, xst portion 0.67 mm., 2nd por- 
tion 4.6 mm. long. Tail curled ventrally ; anus 0.36 mm. from 
tip ; 6 pairs of prse-anal, and 4-6 pairs of post-anal papillse. An 
unpaired dorsal ridge supports the left fold of the tail. Female 
8-11 cm. long. (Esophagus, Ist portion 0.85 mm. long, 2nd por- 
tion 7.8 mm. long. Vulva 4.5 mm. from the tip of tail. Vagina 
extremely long. Ovoviviparous. Embryo provided with a boring 
apparatus. All the above measurements are variable. 
My reasons for creating a new genus are the following : The 
dorsal and ventral sucker-like depressions on the head do not occur 
in any known genus of the Filaridre ; the same may be said of the 
shields; the vulva in the genus Filaria is in the anterior portion of 
the body near the mouth, so our species is excluded from that 
genus ; the genus Spiropte?'a is very indistinctly separated from the 
genus Filaria, but in Spiroptera, too, the vulva is the anterior por- 
tion of the body ; our species cannot enter the genus Dispharagus, 
since a single ovary is supposed to obtain in members of that 
group, and it is excluded from the genus Hystrichis by the absence 
of spines on the head. The other genera of the family Filaridce are 
so totally different from the species under consideration, that I need 
not discuss them. The accompanying illustration was 
drawn from nature by Mr. Hains, one 
of the artists of the Bureau. It shows 
three worms in a portion of the oesoph- 
agus. It will be seen from the figure 
that the worms bore small canals in the 
epithelium, F. female, M. male along- 
side of the female, C. portion of the 
canal formerly occupied by the parasite. 
A complete description of M. 
saUahis, with its pathological effect 
and so much of its biology as has been 
made out, will appear later in the Re- 
port of this Bureau. 
Bureau of Animal Industry, 
U. S, Department of Agriculture, January 5, 1892