MOUSE PLAGUES, THEIR CONTROL AND PREVENTION. 307 



ness to birds and mammals, is out of the question. Among less 

 virulent mineral poisons, arsenic, barium carbonate, lead acetate, and 

 mercuric chlorid give no results warranting their recommendation; 

 moreover, when used on a large scale, they prove quite as expensive 

 as strychnine. 



All things considered, strychnia sulphate is by far the best poison 

 to employ. Properly used, this drug at 75 cents to $1 an ounce is 

 cheaper for the purpose than arsenic at 15 cents a pound. Used on 

 grain it is considerably more expensive than phosphorus, but it can 

 be used on other mediums which make it the cheapest poison avail- 

 able. Tests with a variety of materials show that three possess great 

 advantages as vehicles for poison. These are alfalfa hay, green al- 

 falfa, and crushed wheat. They should be prepared as follows: 



Poisoned alfalfa hay. — Chop 30 pounds of good, fresh alfalfa 

 hay into about 2-inch lengths with a feed cutter. Then place the 

 hay in a large metal receptacle and sprinkle with 3 gallons of fresh 

 water. Thoroughly dissolve 1 ounce of strychnia sulphate in 2 gal- 

 lons of water by heating in a closed vessel ; sprinkle over the damp- 

 ened hay and mix well. (PI. XXIV, fig. 1.) 



Poisoned green alfalfa. — Heat 1 ounce of strychnia sulphate in 

 half a gallon of water until thoroughly dissolved, add to 1 gallon of 

 cold water, and sprinkle this solution slowly over 45 pounds of fresh 

 green alfalfa, cut into lengths of 2 or 3 inches. Mix until the free 

 solution is taken up. 



Poisoned crushed wheat. — Dissolve 1 ounce of strychnia sulphate 

 in 2 gallons of water by heating. Sprinkle the solution over 60 

 pounds of rolled or crushed wheat in a metal receptacle and mix 

 well. If the preparation is to be kept for several days, 2 table- 

 spoonfuls of powdered borax may be added to prevent fermentation. 



Poisoned alfalfa hay proved the best during winter, when green 

 food was absent, and was recommended generally in Humboldt 

 Valley. From January 15 to March 15 it was used extensively in 

 destroying the mice in the area in which they were most abundant, 

 and its use was not attended by a single accident to birds or to 

 animals. From 7 to 15 men were employed on a single ranch in 

 distributing it, placing a small pinch, equal to about a teaspoonful, 

 at the mouth of each burrow, or in cold, rough weather dropping it 

 into the underground runs. In fields where mouse holes numbered 

 10,000 to 24,000 to the acre, there were 10 or more burrows for each 

 mouse, and in fields partially deserted the proportion of unoccupied 

 holes was much greater. Dragging the fields with a brush drag 

 (PI. XXV) to obliterate the holes proved important, for within 

 twenty-four hours the occupied holes were reopened, and poisoning 



