THE CATTLE GRUBS OR OX WARBLES 105 
the grub aperture often retards healing. This may contain the 
_ exuvie of the larve, but usually it seems to be composed of dried 
excretions from the cyst. As the opening heals about this tough 
material there often remains a pit containing a minute hole which 
can be located with a pointed instrument. 
Observations have been carried on to determine the rapidity of 
healing of grub holes in the skin when the grubs are killed by the 
application of insecticides or are extracted by hand. It has been 
observed that where grubs are squeezed out, or even drop normally, 
the old cyst and other material left within it require several weeks 
for absorption. Grubs were extracted on one side of the backs of 
cattle and on the corresponding side they were killed with insecti- 
cides. - Two weeks later these animals were slaughtered and ex- 
amined. The condition of the connective tissue around the grub 
cysts was practically identical on both sides. When the skin was 
removed no discolored or infiltrated tissue was left on the carcass, 
but the former position of the grubs could be located on the under 
side of the hide. The holes in the hide had healed to about the same 
degree with the exception of a few cases in which portions of the 
bodies of the dead larve were in the grub openings, thus preventing 
the closing of the apertures. 
In several herds in which insecticides were administered to the 
backs of the cattle, a number of subsequent examinations were made 
to determine the general condition of the infested areas and the 
rapidity with which the skin healed. In most of these herds the 
erubs were not treated until many of them were nearly mature. 
Seventy-seven days following the treatment it was found that be- 
tween 42 and 62 per cent of the grub holes had healed, and the fact 
that the animals had been infested with larve could not then be 
determined by touch. One hundred and twelve days following 
treatment 75 per cent of the grub holes were completely healed and 
smooth. At this time only 2 per cent remained open and in no case 
was more than a very slight quantity of pus present. In one herd 
treated with benzol it was found that the healing was less ad- 
vanced at the end of 77 days. Only 30 per cent of the grub holes 
were healed and smooth, and 48 per cent of the holes were still open. 
The presence of the grubs was apparent in 25 per cent of the cysts. 
In all cases, however, the warbles were distinctly reduced in size. 
Since in certain animals extraction is greatly facilitated by 
puncturing the grubs and squeezing out their contents before re- 
moving the grub skin, the writers have treated over 200 head in this 
way. Inno instance did the condition of the lesions and the rapidity 
of the healing of the holes in the skin show any difference from — 
those in cases in which the grubs were extracted by squeezing. In 
a number of cattle the grubs were punctured and left in the cyst 
after the body contents had been pressed out. No ill effects were 
observed, but healing of some of the holes in the skin was retarded, 
owing to the hardening in them of the skins of the grubs. One ani- 
mal treated in this way had 60 well-developed grubs in its back. 
Six days after the puncturing, about 10 of the grubs were project- 
ing from the skin. These were shrunken and hardened, and seven 
of these were pulled out. There was no more pus in any of the 
cysts than would occur with living larve. ‘Twelve days later six 
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