percentages of iodine, have unequal amounts of this iodine-free 
material; the latter has a slight but distinct action. 
Results similar to the above were obtained with the thyroid both 
of normal dogs and of dogs which had been fed potassium iodide or 
iodoform. We also found a parallelism between the iodine content 
and the physiological activity of a large number of normal and 
pathological human thyroids. These results will be published in 
detail in another connection, but the following summaries of a few 
experiments with human thyroids may be quoted to show how close 
is the parallelism between iodine content and physiological activity: 
SERIES I.— HUMAN THYROID. 
No. of specimen. 
Gm. thy- 
roid fed 
daily. 
Percentage 
of iodine. 
Mgm. I in 
thyroid fed. 
Fatal dose of ace- 
tonitrile in mgm. 
per gm. 
Recovered. 
Died. 
23927 
0.001 
.001 j 
.001 
0. 05 
.23 
.26' 
0. 0005 
.0023 
.0026 
0. 18 * 
.9 
1.0 
.14 
23821 
23807 
Controls .. 
0.7 
. 95 
.13 
SERIES II.— HUMAN THYROID. 
23927 
0.001 
.001 
.001 
0.05 
.26 
. 45 
0.0005 
.0026 
.0045 
0.08 
.6 1 
.9 
0.096 
.66 
1.00 
23807 -. 
23785 
SERIES III.— HUMAN THYROID. 
23927 
0. 001 
.001 
.001 
0.05 
.23 
. 45 
0. 0005 
.0023 
.0045 
0. 27 
2.0 
3.6 
.21 
0. 28 
23821 
23785 
Controls 
.21 
b. Experiments on Rats. 
The feeding of thyroid to rats lowers their resistance to acetoni- 
trile; the result is thus just the opposite to that which occurs in the 
case of mice. This was, however, the result we had expected in all 
classes of animals. For it seemed probable, if acetonitrile is poison- 
ous only as a result of the liberation of hydrocyanic acid from it in 
the body, that whatever stimulates metabolism would also hasten the 
decomposition of the nitrile, with a corresponding greater production 
of hydrocyanic acid. We do not know whether this is the correct 
explanation of the effect of thyroid feeding in the case of the rat or 
not. Some light upon this question could probably be obtained by 
a study of the excretion in the urine of sulphocyanates. In one 
experiment of this character no difference was found between the 
amounts of sulphocyanic acid in the urine of normal and thyroid fed 
rats after the administration of acetonitrile.® 
a It may be mentioned in this connection that negative results were obtained in 
similar experiments upon dogs. 
