THE CATTLE GRUBS OR OX WARBLES 47 
posited along the back of the thighs, on the escutcheon (fig. 22), 
or on the base of the udder. A number of instances have been 
observed where the soreness and swelling extended down the rear 
quarters to the udder and the tenderness made milking difficult. 
Beneath the skin these swellings are similar in appearance to 
the “ licked-beef ” condition ordinarily found along the back when 
the last-stage larve reach that region. The connective tissue around 
the point of penetration is edematous, tinged with yellow, and some- 
times slightly bloody. 
The scabs become dry within a few days and can be removed. 
Usually a small quantity of hair comes off with them and a num- 
ber of pits are left in the skin indicating the points where the 
larve have penetrated. If the scabs are not removed artifically 
they disappear in the course of a week or two. Animals slaughtered 
during the period of larval penetration have the hides more or less 
damaged at points where 
the larvee penetrate, and 
slight infiltrated areas are 
visible on the carcass. 
As has been stated by 
other writers, these lesions 
may serve as portals 
through which disease or- 
ganisms, such as anthrax 
or tuberculosis, may enter. 
The actions of the ani- 
mals at the time the larvee 
penetrate have been men- 
tioned in a general way. 
The first inclination of an 
animal, after penetration 
on the heel begins, is to 
shake the foot... This is ['# L : 2) 
usually followed by licking Fic. 22.—Iesions on escutcheon of cow, caused by 
(fig. 23), which is often ee ee of newly-hatched larve of Hypoderma 
very vigorous and _ pro- 
longed, and animals have been observed to continue it for two 
minutes without stopping. When the individuals are not allowed to 
lick the heels they usually twist, squirm, kick, and stamp, thus 
showing marked pain or irritation. 
OCCURRENCE IN THE GULLET AND BODY CAVITY 
On account of the minute size and translucent appearance, it is not 
surprising that various investigators have been unable to observe 
the course followed by the first-stage larve after penetration of the 
skin. Stub (95), working in Copenhagen, has given us the only 
definite record. In a post-mortem he observed an infiltrated area 
im the superficial connective tissue on the inside of the right tibia, 
and succeeded in following the track over the shoulder, around the 
muscles of the neck to the tissue on the esophagus, where it enters 
the thoracic cavity. Here he found a number of larve in close 
proximity and measuring 1 to 2 millimeters in length. Hadwen (40) 
