POISONOUS PROPERTIES OF THE WHORLED MILKWEED. 13 



Of the sheep, 534 was only slightly sick, and 372 and 522, in both 

 experiments, showed only symptoms. The average time of the sheep 

 cases was between 4^ and 4| hours, with a minimum of 1 hour and a 

 maximum of 11 hours. The symptoms persisted longer in the more 

 pronounced cases. 



It was shown on page 7 that the A. pumila cases continued from 

 7-| hours to 5 days, and on page 7 that A. verticillata var. geyeri cases 

 varied from 1 to 4 days, averaging 2 days and 8 hours. 



If sheep poisoned by A. galioides recovered they were sick only a 

 few hours, while with both A. pumila and A. verticillata var. geyeri 

 the symptoms continued for a prolonged period. 



Inasmuch as in all the whorled-milkweed cases the symptoms con- 

 tinued longer in the more pronounced cases, and as A. galioides is 

 vastly the most toxic of the three species, one would expect the 

 A. galioides cases to continue the longest. This unexpected result is 

 a matter of a good deal of interest, and there is reason to think that 

 it will be explained by the detailed chemical study of these plants, 

 which is now in progress. 



TOXIC DOSE. 



The leaves and stems of the plant {A. verticillata var. geyeri) were 

 given by the balling gun to 10 sheep. As Asclepias galioides had been 

 found to be extremely toxic, the experiments were commenced with 

 small doses, which were gradually increased until results were ob- 

 tained. No effect was produced until Sheep 473 became very sick 

 on 2.205 pounds per hundredweight of animal. As Sheep 556 was 

 not affected by 2.021 pounds, nor Sheep 546 by 2.113 pounds, it is 

 a fair inference that 2.205 pounds is very close to the toxic dose. The 

 smallest toxic dose of Asclepias galioides is 0.22 pound, while the 

 smallest toxic dose of Asclepias pumila. is 0.787 pound. Asclepias 

 verticillata var. geyeri, then, is about one-third as toxic as A. pumila 

 and about one-tenth as toxic as A. galioides when leaves and stems 

 are fed. 



In feeding the leaves of the plant by the balling gun the smallest 

 dose was 1.286 pounds. The smallest toxic dose of A. galioides leaves 

 fed in the same way was 0.138 pound, so that in this case the A. 

 galioides was about nine times as toxic as the A. verticillata var. 

 geyeri. 



COMPARATIVE TOXICITY OF STEMS AND LEAVES. 



It may be noted that, as shown in the preceding paragraph, when 

 leaves and stems are fed together the toxic dose is 2.2 pounds, while 

 with leaves alone it is 1.378 pounds. This difference, of course, is 

 due to the greater toxicity of the leaves. This is a matter of a great 

 deal of interest, for extended experiments on A. galioides carried 

 on since the publication of Bulletin 800 have conclusively shown a 



