98 BULLETIN 1369, U. S. DEPARTMENT OF “AGRICULTURE 
jected into the cysts; derris used in dry form, as an ointment wit | 
petrolatum, or in suspension in water when injected into the cysts, 
or applied as a wash (///); iodoform and petrolatum, also pyre- 
thrum and petrolatum, when appled as an ointment; and very fine 
tobacco dust and nicotine dust used in powder form. 
The results of the writers’ work seem to indicate rather cleatia 
that the percentage of mortality is not so high in the case of H. bovis 
as with 7. lineatum. 
The treatment of cattle in practice requires the application of a 
method which will be as effective as possible under adverse con- 
ditions. When treatments are given by the livestock owners them- 
selves, washes applied to the entire back of the animal are probably 
the most dependable, in that the inexperienced operator is more 
likely to treat all of the grubs than if the latter have to be found 
individually. On the other hand, there may be some objection to 
the use of washes on the entire back of the animal under certain 
adverse weather conditions. An objection to the use of the syringe 
is that the instrument is an item of expense and may be broken even 
if carefully handled. This tends to commend the oil can if the 
grubs are to be injected individually. In the writers’ experience 
they have found that an oil can with a comparatively slender curved 
point is the most convenient to use. If the aperture in the spout 
is not too large the spout can be utilized to advantage in finding the 
grub hole. One advantage in the use of an ointment such as iodo- 
form-petrolatum is that the operator can easily recognize which 
grubs have been treated. The use of powders is favored by those 
who do not wish to wet the animals during the winter, but some 
objection might be had to them on account of the possibility of the 
dust getting into the buckets duri ing milking. With certain washes, 
however, the dust is left in the hair after the animal has dried. A 
careful application of dust to the backs of cattle is almost as certain 
to reach all grubs as the use of a wash. 
Tobacco infusion has been advocated for the destruction of grubs 
in the backs of cattle by Carpenter, Phibbs, and Slattery (19). 
Although results of the writers’ preliminary tests with similar infu- 
sions were not satisfactory, they continued their experiments after 
receiving Carpenter's favorable reports. In his early publications 
he gave no idea of the strength of the decoctions he used, and it ap- 
pears that he must have employed infusions with a higher percentage 
of nicotine than the writers were able to obtain from American to- 
bacco dusts by using his formula. When, however, tobacco dust 
from the same source as that employed by Carpenter (see Table 11, 
tobacco infusion No. 2) was used, the mortality obtained (65.38 per 
cent) was not nearly so high as reported by Carpenter. With most 
of American tobacco dusts, which run from 1 to 1144 per cent nico- 
tine, great difficulty was found in obtaining an infusion containing 
0.5 per cent of nicotine. In order to get such a percentage the 
amount of tobacco dust advised in Carpenter’s formula was doubled, 
being 8 pounds of tobacco dust, 4 pounds of stone lime, and 1 gal- 
lon of water. In preparing this the lime was first slaked in “the 
water, and then the tobacco dust was stirred in and allowed to stand 
about 24 hours. The mass was then placed in a sack and pressure 
