48 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE 
and stir until a uniformly smooth mixture is obtained. When neces- 
sary the ingredients should be warmed before mixing, so that they 
will mix readily and flow freely. The mixture remains uniform 
without separation or deterioration, and may safely be used on any 
species of domesticated animal. Being of a sticky consistence, it 
remains in the ears and affords protection against reinfestation from 
30 to 60 days. The only known effective method of applying treat- 
ment is to inject the remedy into the ear passages by hand. 
Most horses oppose the insertion of anything into their ears, and 
some form of restraint is necessary. Gentle farm horses can usually 
be controlled with the twitch or other well-known methods of re- 
straint, but in treating wild range horses special equipment is neces- 
sary. An ordinary crowding chute not more than 3 feet wide is 
suitable for treating horses for ear ticks. 
An ordinary metal or hard-rubber syringe holding from 1 to 2 
ounces is the best instrument to use for injecting the pine-tar-cot- 
tonseed-oil mixture. Have the mixture warm enough to flow freely, 
fill the syringe, grasp the ear with the left hand, then insert the 
nozzle into the opening of the ear canal and inject about one-half 
ounce of the fluid. Hold the ear in an upright position for a few 
seconds and manipulate to force the mixture into the deeper parts. 
If too much fluid is injected it will overflow and run down over the 
head and face, where it may cause blistering. The mixture causes 
very little irritation except on parts exposed to the direct rays of 
the sun. 
When the ear passages contain masses of hard wax and ticks, 
such masses should be broken down and scraped out with a wire loop 
before treatment is applied. Treatment should be applied as 
often as necessary to keep the ears free from ticks. One treat- 
ment properly applied can be depended on to kill all ticks in the ears 
and to prevent reinfestation for about 30 days. It should be re- 
membered, however, that the eggs of the tick are not deposited or 
hatched in the ears of animals, and a new crop of seed ticks may 
find lodgment at any time on animals kept in infested places. 
TREATING HORSES FOR EXTERNAL PARASITES 
The three commonly used methods of treating horses, mules, and 
asses for external parasites are (1) hand applications, (2) spraying, 
and (3) dipping. A fourth method, not in common use but recom- 
mended by some European investigators, is fumigation with sulphur 
dioxide. 
HAND APPLICATIONS 
Infested animals may have parasites on any or all parts of the 
body surface, and to effect complete eradication usually it is neces- 
sary to cover the entire surface of the skin with the medicament. 
On account of the difficulty of applying treatment by hand over 
the entire body surface, hand applications are recommended only 
as a temporary measure for holding parasites in check until the ani- 
mals can be dipped or sprayed. 
SPRAYING 
Common parasites on or in the skin can be eradicated by proper 
spraying, but the method commonly practiced is not economical. 
