LARKSPUR POISONING OF LIVE STOCK. 



69 





S /O /5 £0 2S 30 S /O /S 20 2S 30 5 /O 



/OO 

 k 90 



\ «^ 

 b 70 



(A 60 

 30 



















































639 



640 



G93 



--• 











92 















6^y 













1. 

 IIS 





























L 



































632 







6.17 





















i. 



^ 



6fe 









^ 















\63S 







































Fig. 8. — Chart of feeding Delphinium bar'beyi to cattle 

 experimentally poisoned in 1911, showing the dates, 

 quantities fed, and duration of feeding. e indicates 

 plants collected near station ; X indicates plants col- 

 lected at Kebler Pass about 1,000 feet higher than the 

 station ; those marked L received leaves ; the others 

 were fed the whole top of the plant. 



95.8 pounds. The cases of 1911, all being of Delphinium harheyi 

 poisoning, averaged 63.3 pounds. 



It was the impression among the observers at the station during the 

 first two seasons that about one-tenth the weight of the animal was 

 the toxic dose, and it 

 is certainly rather 

 remarkable that the 

 averages come so 

 close to that quan- 

 tity. A careful study 

 of the cases of the 

 three seasons, how- 

 ever, shows not only 

 that in the average 

 case this is an over- 

 estimate, but that 

 there are two factors 

 which profoundly 

 modify the quantity 

 necessary to produce 

 poisoning in indi- 

 vidual cases. One 



factor, the seasonal variation in tlie toxicity of the plants, is dis- 

 cussed under a special heading on page 75. The second factor is the 

 length of time during which the plant was fed. This is indicated in 

 charts 11 to 14, and it will be noted that in general the size of the 



toxic dose increases 

 with the time during 

 which the animal is 

 fed. This is shown 

 in a striking way in 

 the animals poisoned 

 by Delphinium har- 

 heyi in 1909. After 

 tabulating the num- 

 ber of days of feed- 

 ing and the quanti- 

 ties fed, and making 

 averages of the cases, 

 it was found that of 

 the animals poisoned 

 by 1 day's feeding, 

 the average quantity was 53.2 pounds; of those poisoned by 2 days' 

 feeding, 82.1 pounds; of 3 days' feeding, 133.7 pounds, and of 4 

 days' feeding, 160.1 pounds. The averages for the other two years 

 show the same thing but not so clearly, as the seasonal variation in 





20 2S 30 5 10 IS ZO ZS 30 S '0 /S 20 



120 



k "° 



^ /OO 

 (0 BO 



i ^"^ 



^ 60 

 SO 









































-^ 





















■ 



jO) 



-9 







m 

























1/7 









- 



^6/4 



























jMj 























































^3 







































































Fig. 9. — Chart of feeding of Delphinium menziesH to cattle 

 experimentally poisoned in 1910, showing dates, quanti- 

 ties fed, and duration of feeding. The short horizontal 

 line indicates duration of feeding. The weights of plant 

 are given per thousand pounds of animal. 



