56 
C. CONTROLS.** 
Date. 
1 Weight j 
of mouse. 
Remarks. 
1907. 
December 5. . . 
17. 55 
Feeding of cakes without thvroid begun. 
9... 
17.38 
12... 
17.54 
14... 
17.93 
15. . . 
17.80 
Acetonitrile, 3.03 mgms., i. e., 0.17 mgm. per gm. mouse. Survived. 
December 5. . . 
15.33 
Cakes as above. 
9... 
15.88 
12...; 
16.25 
14... 
16.52 
15... 
15.97 
Acetonitrile, 3.03 mgms., i. e., 0.19 mgm. per gm. mouse. Died 1J hours. 
December 5. . . 
17.31 
Cakes as above. 
9... 
17.91 
12...; 
17.53 
14... 
18.12 
Acetonitrile, 3.81 mgms., i. e., 0.21 mgm. per gm. mouse. Died 2 j hours. 
December 5. . . 
15.09 
Cakes as above. 
9... 
15.24 
12... 
14.85 
14... 
15.06 
Acetonitrile, 3.77 mgms., i. e., 0.25 mgm. per gm. mouse. Died 6J hours. 
a It will be noticed that the fatal dose of acetonitrile for the mice of this series was less than one-half as 
large as that for those of the preceding series. Such variations in susceptibility are frequent and are largely 
the result of diet, differences in age. weight, etc. : it illustrates the necessity for using only those mice which 
have been kept under identical conditions and also the necessity for many controls. 
Summary . — The results of the above experiments may be sum- 
marized as follows: 
Gm. 
thyroid fed 
daily. 
Percentage 
of iodine 
in thyroid. 
Mgm. I in 
thyroid fed 
daily. 
Fatal dose of aceto- 
nitrile in mgms. 
per gm. 
Recovered. 
Died. 
A 
B 
C. Controls 
0.004 
.002 
0.087 
.17 
0.00348 1 
.0034 
2.3 
2.3 
.17 
2.5 
2.4 
.19 
When two parts of A (0.087 per cent iodine) and one part of B 
(0.17 per cent iodine) were fed, equal physiological effects were 
produced. 
Series III. 
In this series both of the methods referred to above were em- 
ployed, i. e., equal amounts of thyroid containing different amounts 
of iodine and different amounts of thyroid containing equal amounts 
of iodine were given. Unfortunately we are not absolutely certain 
that the analytical data are entirely correct for one of the prepara- 
tions, viz, that stated to contain 0.061 per cent of iodine. This was 
the figure obtained on the analysis of a sample taken from the sur- 
face of the bottle; later analyses of the thoroughly mixed contents 
of the bottle showed 0.1 per cent iodine. Inasmuch as the physio- 
logical activity of the surface layer corresponded to that of thyroid 
