4 BULLETIN 1369, U. 8. DEPASPARTFMENS) aGRICULTURE 
in Holland, gave definite proof that the small larve found in the 
spinal column of cattle were really Hypoderma. Some of these were 
introduced under the skin of a goat, and 12 days afterwards swellings 
appeared, from which later 1. bovis was reared. In the same article 
he also described experiments in which 26 larve from the spinal 
canal of cattle were introduced under the skin of a dog. When the 
animal was examined two weeks later some of the larve were found 
in various parts of the animal, including the gullet and spinal canal. 
Similar larve fed to dogs and introduced into the gullet of a rabbit 
through a tube were not recovered. From these tests Koorevaar 
concludes that in bovines the larvee reach the gullet or spinal canal 
after extensive wanderings from the place where they bored through 
the skin, and that they do not reach the gullet by way of the mouth. 
Further studies on the migration and seasonal occurrence of the larve 
within the host were published the same year by Koorevaar (55). 
Following the publication by Curtice and the subsequent one by 
Riley, practically all scientists accepted Curtice’s theory. In 1903 
Koch (53) published a very valuable contribution as the result of 
several years’ study of the larve of Hypoderma within the bodies 
of cattle. He shows that the young larve are widely distributed 
within the body cavity and in the intermuscular tissues of the back, 
and that larvee as small as 2.2 millimeters in length may be found 
in the submucous tissues of -the gullet. He concludes from the 
data presented that— 
It will presumably be apparent that the entrance of Hypoderma larv# to 
the bodies of the cattle takes place through the alimentary system and not 
through the skin, and further that the larve migrate through the cesophagus 
and vertebral canal to the skin. 
In 1907 Jost (52) reviewed the life history of HY. bovis. He con- 
cluded that the eggs hatch in the gullet and that the larve bore 
through the mucous lining of it. He also makes the erroneous 
statement that the life cycle requires about nine months. Sdérensen 
(93) in 1908 discussed the literature and concluded that the larvee 
enter by mouth. 
During the period 1908 to 1922, Carpenter and his associates in 
Ireland published a series of papers (/2 to 19) dealing especially 
with experiments with the muzzling of calves in an effort to prevent 
their infestation. The earlier results were conflicting and the 
authors changed their viewpoint from year to year. In 1914, how- 
ever, Carpenter, Hewitt, and Reddin (77) published the results of 
their observations on the penetration through the skin of larve of 
both H. lineatum and H. bovis. They first noticed soreness and 
scabs in the regions near where eggs of Hypoderma were attached. 
Beneath these they found holes indicating penetration and from 
one of these was squeezed, along with serum, a first-stage larva of 
H. lineatum which had evidently penetrated through the skin at 
the spot. They followed this with tests of newly hatched larve of 
H. bovis placed on clipped hair on a calf and found that they quick- 
ly passed down the hair and began to burrow into the skin immedi- - 
ately. They conclude: 3 | 
We believe therefore that no further doubt is possible as to the entrance of 
young Hypoderma larve into its host through the skin close to wherever the 
eggs may have been laid, and the results of the muzzling experiments show 
that entrance by the mouth is unlikely. 
