164 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
load lots at the present time, but if a demand is created it will 
no doubt be available in smaller quantities. In the commercial 
fertilizers it is usually converted into urea, ammonia, etc. Of 
the various substances tested, the most satisfactory results were 
obtained with powdered hellebore and borax. One-half pound 
of powdered hellebore is mixed with 10 gallons of water and 
allowed to stand 24 hours. This quantity is sufficient to treat 
10 cubic feet (8 bushels) of manure, being applied with a 
sprinkler. The borax is applied with a flour-sifter, especially 
around the edges of the manure heap, and water is then sprinkled 
over it; about 1 ounce of borax and 21% to 8 quarts of water 
are used to each cubic foot of manure. Floors, crevices, and refuse 
may be treated in the same manner with either hellebore or borax. 
Borax is perhaps a little more effective as a larvecide than 
hellebore, but the latter is not at all injurious to the manure nor 
to crops while borax in excessive quantity interferes with plant 
growth. Manure treated with borax as above may be applied 
in any quantity up to 15 tons per acre without injuring the 
crops, except in the case of leguminous plants. When borax- 
treated manure is used to grow leguminous plants, it should be 
mixed with untreated manure. The effect of the repeated appli- 
cation of borax-treated manure has not been determined. The 
cost of treating manure with powdered hellebore is a little over 
1% cent per bushel, while the expense of the borax treatment 
is a little less than 14 cent per bushel. 
The cow-fly or horn-fly lays its eggs in fresh cow manure. 
The larve are hatched in 24 hours and develop into pupe in 5 
days. The pupz burrow into the ground and flies emerge in 8 
days, the time from the egg to the fly being 14 days. 
These flies feed upon the blood of the cow and are therefore 
not likely to get into the milk or milk vessels. In biting through 
the skin of the cow to obtain food, they cause the animal con- 
siderable discomfort. When driven off the body of the cow, they 
fly only a short distance away and then immediately return, so 
that, while feeding, they are a continual torment. 
Fly repellents are used to protect the cow from the attacks 
of these insects. A mixture of one part of oil of tar and nine 
parts of cotton-seed oil or crude Beaumont oil, applied daily 
