PARASITES OF THE ALIMENTARY TRACT 71 
dust. Each egg is ovoid, about go p long, and provided 
at one end with an operculum. 
Symptoms—These are often absent. When the 
worms are present in large numbers there is seen 
frequent rubbing of the anus and tail, with the presence 
of the characteristic yellow dust around the anus. 
Occasionally there is loss of condition from irritation 
and loss of rest. Oxyuris mastigodes appears to cause 
more disturbance than Oxyuris curvula. 
Life-History—This has not been fully worked out. 
Probably there is no intermediate host, but infection by 
ingestion of ova. 
Treatment.—Turpentine and linseed-oil given once a 
week or once a fortnight, with early-morning clysters 
of infusion of quassia or common salt, given after the 
rectum has been emptied by hand, usually eradicate 
these parasites. 
The ‘‘ worm-powders,” of which the prescription was 
given when referring to Ascarides, are very useful. 
Trematodes occurring in the Horse. 
These are two in number: 
1. Amphistomum Collinst. 
2. Gastrodiscus Algyptiacus. 
Amphistomum Collinsi (Masuri).—This is a worm of a 
brick-red colour occurring in immense numbers in the 
large intestine of horses in India. They produce great 
irritation. 
Gastrodiscus Higyptiacus (Gastvodiscus Sonsinoi, Gas- 
trodiscus Polymastos).—This parasite has a red, oval 
body, about 12 millimetres long, convex on the upper 
or dorsal and flat on the ventral surface. The buccal 
sucker is carried on a short proboscis, while the ventral 
surface carries about 200 papillary suckers. 
It inhabits chiefly the small intestine of horses, asses, 
and mules in Egypt and Senegal, but may occur in 
