9 
to foliageis not shown at once, and in case of rain following an application 
another application should not be made for several days. Fruit trees 
should not be sprayed with arsenical poisons while in blossom, as there 
is no advantage in doing so, and honeybees are reported to be at 
times killed by working in the sprayed blossoms. 
SPRAYING FROM THE HYGIENIC STANDPOINT. 
The only insecticide sprays which are at all dangerous to use are the 
arsenic compounds, and even here the danger is greatly exaggerated by 
those not conversant with the facts. Paris green and London purple 
have for many years been extensively used in this country as insecticides 
and a case of fatal poisoning from their use as such has never been sub- 
stantiated. The only danger lies in having the poison about a farm or 
plantation in bulk. In the early days of the use of Paris green against 
the Colorado potato-beetle a great deal of opposition was developed on 
account of the supposed danger, and only recently the sale of Ameri 
can apples in England has received a set-back owing to the supposed 
danger of arsenic poisoning from their consumption. The question as 
to whether arsenic may be absorbed by the growing plant in any degree 
was long ago settled inthe negative by the best chemists in the country. 
Dr. William McMurtrie, formerly chemist of this Department, in 1878 
showed that even where Paris green was applied to the soil in such 
quantities as to cause the wilting or death of the plants, the most rig- 
orous chemical analysis could detect no arsenic in the composition of 
the plants themselves. Other experiments in a similar direction by 
Prof. R. C. Kedzie, of the Michigan Agricultural College, confirmed 
these conclusions. It is safe, then, to assume that the only way in 
which fruit or vegetables can convey the poison to the consumer will be 
through the very minute quantity of arsenic left upon the edible part 
of the plant. Against the possibility of such an effect the following 
facts may be urged: 
(1) It would seem at first glance thatthe use of an arsenical poison upon 
a plant like the cabbage would be very unsafe to recommend, yet Paris 
green and London purple are used upon this crop to kill the several 
species of leaf-eating worms which are so destructive to it, and an ab- 
‘solute absence of all danger where the application has been properly 
_made has been recently shown by Prof. Gillette, of the Agricultural 
Experiment Station of Colorado, by the following reductio ad absurdum: 
* * * Where the green is dusted from a bag in the proportion of 1 ounce of the 
poison to 100 ounces of flour and just enough applied to each head to make a slight 
show of dust on the leaves, say, for twenty-eight heads of cabbage, 1 ounce of mix- 
ture, the worms will all be killed in the course of two or three days, while the aver- 
age amount of poison on each head will be about one-seventh of a grain. Fully 
one-half of the powder will fall on the outside leaves and on the ground, and thus 
an individual will have to eat about twenty-eight heads of cabbage in order to con- 
sume a poisonous dose of arsenic, even if the balance of the poison remained after 
cooking. 
