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on the evolution of the generative system. In two of the animals so infected,
the eggs appeared in the fæces on the 50th day and in a third did not appear
till the 53rd day. The histopathology of the intestinal tissues is also dealt
with. The nodules which were undergoing necrosis showed a diminution in
size and in inflammation after the emergence of the fourth-stage larvæ, and
disappeared in 35 days.
With the material obtained by Veglia for his studies on O. columbianum,
Fourie [ 1936] investigated the pathology and pathogenesis of the disease.
Enriched by a set of illustrations of a high order, the paper deals with every
stage in the formation of the nodule and the reactions of the intestinal tissues
to the entry of the larvæ.
In his ' Parasites and parasitic diseases of domesticated animals ' Neu-
mann [ 1892 ] mentions Drechsler's discovery, as far back as 1876, of some 450
nodules of varying sizes beneath the mucous membrane of the intestines of an
ox, most of which had caseated. ' Spherical in shape, and well-defined, they
were composed of strong fibrous tissue, and each contained an undetermined
nematode—or rather a larva—about 1 mm. long, and which had two conical
cephalic papillae. These were probably the larvæ of Strongylides '. Cleland
[ 1907] from Australia obtained similar nodules from the intestines of a
slaughtered bullock and larvæinside them which agreed to the above descrip-
tion except that the cephalic papillae were not distinct and the size was smaller.
The first milestone in the study of nodular disease in cattle was crossed
when Marotel [ 1908 ] conclusively demonstrated the identity of the larval
parasite as an Oesophagostomum. The species in France which is responsible
for the nodules was also revealed by him as O. radiatum. On a considera-
tion primarily of the organization of the oral structures he distinguished three
successive stages of the larvæ as strongyliform, ankylostomiform and oeso¬
phagostomiform. The strongyliform larva has a small narrow mouth, the
ankylostomiform larva an elliptical mouth with a solitary tooth, and the
œsophagostomiform larva with a cuticular inflation in the ventral cervical
region. After a period of development inside the nodule they return to the
lumen of the intestine to mature, copulate and reproduce.
Jowett [1911 and 1912 ], comparing the nodular disease of bovines with
that of sheep in Africa, recorded the appearance and location of the nodules
in the sub-mucosa of the small intestines and frequently in the colon also. He
has attempted to follow the life-cycle of the parasite, with a knowledge of
the Oesophagostome in man and monkey. When, in time, the nodules
rupture, the larvæ are liberated into the intestine and evolving into females
and males copulate and lay fertilized eggs. The eggs, segmented even during
their passage in the uterus, reach the soil with the host's fæces and larvate.
The larva contaminates the soil, food or water and gains entry into the host.
' It then burrows into the lining membrane of the gut, or, according to some
authors, reaches the ultimate site it occupies in the sub-mucous tissue by
means of the blood-stream. Be that as it may, the embryo is finally arrested
in the sub-mucous coat of the intestine, where it gives rise to the formation
of a hæmorrhagic cyst—the nodule so characteristic of the disease'. The
implication that the larvæ may undergo a migration with the aid of the blood
before the nodule-formation is evident, though the migration has been proved