28 N. H. AGR. EXPERIMENT STATION, [Bulletin 183 



than so-called toxic doses lead and arsenic have deleterious 

 effects on cell protoplasm, effects that are expressed in lowered 

 resistance to disease, lessened efficiency, and shortening of life." 



RESULTS OF FEEDING LEAD ARSENATE AND WHITE ARSENIC TO 



GUINEA PIGS. 



It has been shown that the maximum amounts of arsenic found 

 by analysis are: for apples .3 to .8 milligram per fruit; for small 

 fruits 2 to 8 milligrams per portion of one-fourth quart; for cab- 

 bage 45 milligrams per head; and for lettuce 6 to 10 milligrams 

 per head. These we are to interpret in their relation to the 

 ordinary standards which cite 1 to 5 milligrams as a medicinal 

 dose of white arsenic, AS2O3, and 60 to 120 milligrams as a dan- 

 gerous dose. It has been shown, also, by the results of the 

 determinations made at the Hull Physiological Laboratory in 

 behalf of this investigation, that the arsenic in arsenate of lead 

 is not in a highly soluble form in human gastric juice but prob- 

 ably in that medium is less soluble than is arsenic in the form of 

 white arsenic. 



To help in arriving at a correct interpretation it was now pro- 

 posed: 



(1) To feed to small mammals daily doses of arsenate of lead 

 equal to the average maximum found on sprayed apples, increas- 

 ing the amount from time to time up to the point of fatal poison- 

 ing. 



(2) To feed to parallel lots of small mammals equal amounts 

 of lead arsenate and of white arsenic, in order to establish some 

 basis of comparison between the toxic properties of these two 

 substances. 



With this double object in view, experiments were begun in 

 feeding, directly, known amounts of lead arsenate and white 

 arsenic to guinea pigs. 



Pens were constructed in the open air insectary belonging to 

 the department. This is a building in which a fairly constant 

 temperature is maintained thruout the year. In summer the 

 sides are of gauze wire. In winter, glass sash are substituted for 

 the gauze wire, 9,nd steam heat, under thermostat control 

 maintains a temperature reasonably constant. 



The guinea pigs secured were of apparently uniform good 

 health and varied in weight from 16 to 23 ounces. They were 



