April, '13] ARSENICAL RESIDUES DISCUSSION 159 



Apparently different lots prepared by the same manufacturers differ 

 considerably in regard to injuriousness to plants. The "Ortho" 

 brand arsenite of zinc is now recommended by the manufacturers 

 to be used with equal parts of commercial iron sulphide. This is 

 said to neutralize the injurious effects. 



President W. D. Hunter: Any further discussion. The chair- 

 man believes that Dr. Ball is not present. The next paper is by 

 W. C. O'Kane, on "Arsenical Residues on Fruit." 



ARSENICAL RESIDUES ON FRUIT 



By W. C. O'Kane, Durham, N. H. 

 (Withdrawn for publication elsewhere.) 



President W. D. Hunter: Any discussion on this paper? 



Mr. E. p. Felt: I was interested in the paper because for some 

 years questions have been coming to me along that line. We all 

 know that the amount of arsenate of lead used for spraying shade 

 trees has been increased. Our experiments show that arsenate of 

 lead remains on the trees some time. I believe in using poisons, 

 and even after hearing the evidence, we should all be careful and not 

 advise the use of too much. 



]\Ir. C. L. Marlatt: I would like to inquire as to the cumulative 

 effects of arsenate of lead. 



Dr. Hall : In reply to this question I will say as a physician, and 

 not as an entomologist, that arsenic is a drug that one can get a toler- 

 ance for. Small quantities act as a tonic and the amount that can 

 be taken without showing any serious effects can be increased from 

 time to time. 



Mr. R. W. Braucher: In regard to animals being injured by lead 

 poisoning, I will say that in an orchard where I worked last summer 

 one cow was killed and two made sick. Investigation showed that 

 the trouble was not caused from spraying but was due to the animals 

 licking the dry residue on the inside of some of the barrels which 

 had contained lead and which were carelessly placed on a dump in 

 the pasture. 



Mr. a. F. Burgess: I would like to make one suggestion in regard 

 to the results of experiments given in the paper by Mr. O'Kane. 

 You will note that the spraying was carried on in August shortly 

 after the small brown-tail caterpillars had hatched. Such spraying 

 of course, leaves a heavy residue on the foliage and fruit, but it is 

 not necessary to spray at this season of the year except in regions 

 where the brown-tail moth exists. In nearly all the orchard sections 



