﻿EIGHTH A>'NUAL REPORT 



bug machines," or their glib agents. The National Academy, after the- 

 reading of Dr. LeOonte's paper, appointed a committee to " investi- 

 gate and report upon the subject o' the use of poisons applied to veg- 

 etables or otherwise for the destruction of deleterious insects and 

 other animals," etc. ; but that committee has, I believe, made no re- 

 port yet. Prof. R. C. Kedzie, of the Michigan Agricultural College 

 did, however, carry on a series of interesting experiments last sum- 

 mer, and while visiting the college in August I bad the pleasure of 

 witnessing and making notes of ihe Professor's operations. As he has- 

 since given these results to the American Public Health Association, 

 and published an abstract of them in ihe Detroit Free Pret<fs^ I take 

 the liberty of giving them wider circulation. 



First, as to the use of the mineral for the Doryphora. Does Paris- 

 Green poison the tuber? Tubers taken from vines that had been re- 

 peatedly dosed with the ordinary mixture— as much Paris Green, in 

 fact, as they would bear — gave no trace of arsenic. Regarding the 

 idea, which has been suggested, that the use of the poison rendered 

 the tubers watery and waxy, the conclusion is that such condition is. 

 brought about hy the stunted growth and destruction of the vines- 

 caused by the insect, which thereby prevents maturity of the tuber^ 

 Does Paris Green poison the land? This is meant, of course, in the 

 sense of rendering the land unfit lor the growth of crops; and ProL 

 Kedzie justly considers not only its immediate, but its remote eifect. 

 Theoretically, one would naturally infer that Paris Green is con- 

 verted into an insoluble precipitate or salt with the hydrated oxide of 

 iron which exists in most soils ; but not resting the matter on theoreti- 

 cal or abstract reasoning. Prof. Kedzie made careful tests and experi- 

 ments. He passed a solution of arsenious trioxide through common 

 garden soil, and filtered Paris Green in a solution of hydrochloric acid 

 through dry earth. In neither case could any poison be detected irk 

 the filtrate by the severest tests. Soil taken from a field of wheat 

 that had been sown with Paris Green at the rate of five pounds to the 

 acre showed no trace of the poison when submitted to any or all of 

 the tests which the soil would get by natural solvents in the field, but 

 distinctly sliowed the ars.enic when treated with dilute sulphuric acid. 

 The Paris Green was sown on the ground early in Spring, and was 

 thick enough to give a very distinct green tint to the surface. The 

 grain and the straw were submitted to careful chemical examination, as 

 were also cabbages grown in soil that had the year before been in 

 potatoes and received a heavy sprinkling of Green. ISo trace of the 

 poison was found in either, and it was observed that the chipmunks 

 ate large quantities of the grain without injury. The more practical 

 conclusions from Prof. Kedzie's experiments may be thus summed up: 



