40 
Table IV. — Determination of the minimum lethal dose for Rana pipiens, twelve-hour 
' method — Continued. 
SUMMARY. 
Preparation. 
M. L. D. a 
B. W. and Co. 
c. c. mgm. 
0.015=1. 5 
Mulford No. 2 
. 020=2. 0 
S. and D 
. 027=2. 7 
P., D. and Co 
. 029= 2. 9 
a M. L. D.=minimal lethal dose. 
Factors modifying effect . — Our experiences with the various factors 
which are supposed to influence the reaction of the frogs may be 
briefly summarized here. 
Weight.— In regard to the weight of the animal many workers have 
apparently very largely ignored this factor, while others have made 
only an approximate allowance for it. For instance, Focke says to 
use frogs weighing from 25 to 30 grams, while others merely say 
“large” frog or “medium” or “small,” as the case may be. In our 
experience, which covers some years, we have always weighed the 
animals fairly accurately, within the limits of 1 gram, and then calcu- 
lated the dose per gram body weight.® This seems not to be abso- 
lutely necessary, judging from the reports of several writers quoted, 
but we think that it can not help but insure greater uniformity in the 
results, especially when there are certain factors such as idiosyncrasy 
which can not possibly be allowed for. 
Sex . — Our experiences agree with those of Focke that unless it is 
in the springtime there is no particular difference in the reaction 
obtained from male and female frogs. 
Season . — The effect of the season of the year upon the conditions 
of the frogs seems to be pretty generally recognized. Both Mosch- 
kowitsch and Dixon point out that the frogs are most active in the 
spring. The question has been most fully considered by Focke, who 
says that on account of the seasonal variations only summer frogs 
should be employed, as they not only react differently at this time but 
there is very much less variation in their reaction. According to a 
later research, * * * 6 if they are to be used at any other season, they should 
themselves be standardized by testing them against a digit alis prepa- 
ration of known value and using the temperature factor which will 
give the preparation its standard “V” as previously determined. 
The introduction of this factor, however, we believe to be entirely 
unnecessary excepting that comparative experiments should be car- 
a In our former work we used as a standard for comparison doses calculated on the 
basis of a 20-gram frog, but in this work we have compared the preparations upon the 
basis of 1-gram body weight as being simpler. 
& Focke, Arch. d. Pharm., 1907, CCXLV, 646. 
