LARKSPUR POISONING OF LIVE STOCK. 
69 
S /O /S 20 25 30 5 /O /S 20 25 30 5 /O 
/OO 
K 90 
K 
la 70 
Q 
(« 60 
| 5° 
30 
635 
640 
&f3 
■•9 
92 
&tr 
L 
115 
L 
632 
y 
L 
&f4 
6f€ 
— ( 
' 
r.635 
J 
Fig. 8. — Chart of feeding Delphinium barbeyi to cattle 
experimentally poisoned in 1911, showing the dates, 
quantities fed, and duration of feeding. o 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 barheyi 
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 the 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 bar- 
beyi 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 
M*V « JC/A/S k JUL V 
20 25 30 5 IO IS 20 25 30 5 10 IS 20 
/20 
k "° 
\ /OO 
K 
h 90 
| 70 
% 60 
SO 
J2 
J0> 
•% 
<j* 
1/7 
-* 
r 6/4 
~ * 
m 
Fig. 9. — Chart of feeding of Delphinium menziesii 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. 
