June, 1917.] arsenical residues after spraying. 31 



RESULTS AND DISCUSSION. 



In Table No. 7 are set forth the results of feeding lead arsenate 

 beginning with relatively small doses, continuing such doses 

 daily, for 30 days or sometimes less; then permitting a resting 

 period; then again resuming the poison, but with a heavier dosage; 

 then, again, a resting period; again resuming the poison, with a 

 still heavier dosage; and continuing this, up to serious illness or 

 death of the pig. A cross at the end of a line indicates the death 

 of the pig. 



It will be observed, at once, that pigs receiving 1 unit, 2 units 

 or 3 units daily, for a period of 30 days showed no evidence of 

 fatal poisoning. When such pigs were placed on a daily dosage 

 of 4 units, 5 units and 6 units daily, they still showed no fatal 

 poisoning; when the dosage was increased to 7 units the pigs 

 still survived. 



The first case of fatal poisoning occurred when 8 units were 

 fed. From that point on up to 13 units, fatal poisoning occurred. 



In Table No. 8 are shown the effects beginning with a heavy 

 dosage in the daily feeding, without any preliminary period of 

 lighter dosage. This series of experiments was undertaken in 

 view of the possibility that the pigs recorded in Table No. 7 

 might have reached safely a dosage of 8 units daily because of 

 acquired tolerance, resulting from earlier feeding with lighter 

 doses. 



In this table it will be observed that in one case, No. 18, the 

 administration of 8 units daily for a period of 22 days was followed 

 by the death of the pig. With pig No. 46, the administration of 

 6 units daily for a period of 38 days was followed by the death of 

 the pig. Doses of less amount than these did not result fatally, 

 except with pig No. 37, who received 4 units daily for a period of 

 25 days and died. 



On the whole, the dosage point at which fatal poisoning is apt 

 to occur appears to be similar to that found with pigs that had 

 first received lighter doses thru considerable periods. In other 

 words, there is no marked evidence of acquired tolerance. 



In Table No. 9 are set forth the results where equivalent units 

 are fed in the form of white arsenic AS2O3, instead of lead arsenate. 

 In this case, fatal results began with a dosage of 4 units, adminis- 

 tered thru 14, 15 and 20 days, respectively, as shown by the 



