27 
of thyroid which produces a physiological effect. It is evident, how- 
ever, from the above that as little as 0.1 mgm. of dry thyroid fed 
daily for eleven days produced a marked effect ; still smaller amounts 
would doubtlessly have produced a distinct effect. 
As was shown in a previous paper,® this reaction of mice is a very 
delicate test for thyroid. A few milligrams of thyroid mixed with a 
large amount of blood or of toasted bread, tamarinds, liquorice 
powder, etc. (as in the case of a number of the secret “ antifat ” nos- 
trums), may readily be detected. We have found no other sub- 
stance with an effect upon the resistance of mice to acetonitrile at 
all comparable to that of thyroid. This physiological test for thy- 
roid is far more delicate than any chemical method for its detection. * 6 
In most of our experiments the thyroid was fed for nine or ten 
days before the injection of the nitrile. This period was selected in 
part arbitrarily and in part because we were convinced that it was 
sufficiently long for the maximum effect of the thyroid to have been 
produced. A very distinct effect was, however, present in a much 
shorter time; thus mice which had received rather large amounts 
of an active thyroid preparation for but two days recovered after the 
injection of twice the dose of nitrile fatal to the controls. 
We have few data as to how long the effect of the thyroid continues 
after the feeding is discontinued. We have observed in some cases, 
however, that the increased resistance persisted, although it was less, 
for at least two weeks. 
Conditions influencing the resistance of mice to acetonitrile. — Dif- 
ferent groups of mice vary in their susceptibility to acetonitrile; 
hence in carrying out a series of experiments with this substance it 
is absolutely indispensable to have mice* which have been kept under 
uniform conditions. In testing the effect of thyroid it is also necessary 
to have a number of controls for each series of experiments. With 
these precautions we have rarely failed to obtain entirely concordant 
results and have as a rule determined the fatal dose of the nitrile 
a R. Hunt, J. Am. M. Ass., 1907, 49, p. 240. 
& As was pointed out in the paper referred to above, this method seemed adapted 
to throw some light on the question whether there is an excessive amount of thyroid 
secretion in the blood in cases of Grave’s disease. So far we have been able to test 
the blood in only three such cases. In one of these the blood had a marked effect in 
increasing the resistance of mice to acetonitrile, indicating an excessive amount of 
thyroid secretion. In another case the results were doubtful; the amount of blood 
was insufficient for even two experiments. In the third case the results were nega- 
tive. Possibly this test may have some diagnostic value, although on the thyroid 
theory of Grave’s disease it is not necessary to assume that an excess of thyroid secre- 
tion is present in the blood at all times. So far as our observations go it is probable 
that the best results would be obtained by administering 1 or 2 c. c. of the blood to 
mice daily for nine or ten days before testing with the nitrile. Several controls 
(mice fed with normal blood) are indispensable. 
