PARASITES OF THE ALIMENTARY TRACT 63 
or in dung at ordinary room-tempera- 
tures require twenty-four to thirty days 
for the complete development of the 
embryos, but if incubated at 37° C. 
three to four days is sufficient. He 
infers that transmission of the parasite 
takes place without an intermediate 
host by ingestion of ova in dung. He 
fixes the age at which the Ascaris gains 
sexual maturity as from ten to twelve 
weeks. Foals are particularly subject 
to Ascarides, but they occur in horses 
of all ages. Although no worms may 
have been passed in the dung, their 
existence may often be demonstrated 
by the presence of ova in the faces. 
They are rounded, and easily visible 
when a portion of the feeces containing 
them is mixed with a small quantity 
of water on a glass slide and exposed to 
a magnification of roo diameters. 
Symptoms.—Usually the symptoms 
are nil, but when large numbers are 
present anemia and marasmus may 
result. Intestinal catarrh is often asso- 
ciated with their presence, and is indi- 
cated by the discharge of a small 
quantity of watery fluid after defeca- 
tion. 
More uncommon is peritonitis, pro- 
duced by perforation of the intestinal 
wall. Jaundice has occasionally been 
seen, owing to the passage of an Ascaris 
up the bile-duct, but this is rare. 
In foals particularly, large numbers of Ascarides not 
infrequently form a bundle and cause obstruction. 
Fic, 16.—ASCARIS 
MEGALOCEPHALA, 
