77 
These results show that in order to cause approximately equal 
physiological effects (as measured by the diminished resistance of the 
rats to acetonitrile) it was necessary to feed larger amounts of the 
iodine poor than of the iodine rich thyroid. 
Series III. 
In this series the physiological activity of dog thyroid, the iodine 
content of which had been increased by the administration of iodo- 
form,, was determined. As the results of these experiments are given 
in detail in Part II (p. 103-5) of this bulletin, only a summary will 
be given here. 
Gm. thy- 
roid in 
each cake. 
Percentage 
of iodine. 
Mgm. I in 
thyroid of 
each cake. 
Fatal dose of aceto- 
nitrile in mgms. 
per gm. 
Recovered. 
Died. 
A 
0. 0005 
0.111 
0. 00055 
1.8 
2.1 
B 
.0005 
.300 
. 00150 
1.3 
1.5 
c 
.0015 
.111 
. 00166 
1.2 
1.3 - 
D 
.003 
.111 
. 00333 
.9 
1.0 
E 
.001 
.300 
. 00300 
.5 
.6 
F. Controls 
2.9 
3.0 
1 
GENERAL CONCLUSIONS. 
The above series of experiments show that there is a close parallel- 
ism between the iodine content of the thyroid and its physiological 
activity as measured by its effect in diminishing the resistance of 
rats to acetonitrile. 
2. EXPERIMENTS WITH MORPHINE. 
It has been shown above that the feeding of thyroid causes an altera- 
tion in the resistance of animals to acetonitrile. The effect differs 
in different species; there is an increased resistance in the case of 
mice and diminished resistance in rats. In both cases, however, the 
activity of the thyroid is parallel with its iodine content. 
Experiments will now be described in which the effect of feeding 
thyroid upon the resistance of animals to another poison, morphine , a 
was determined. Experiments were made upon mice, rats, and 
guinea pigs. The resistance of all of these animals to morphine was 
lowered by the feeding of thyroid and there was a general parallelism 
between the activity of the different thyroid preparations in this 
respect and their iodine content. 
In performing experiments with morphine it is necessary to observe 
the precautions noted in the experiments with acetonitrile. Different 
a Similar results were obtained in a few experiments with acetyl-morphine (“heroin ”) 
and with codeine. 
