19 
Marine and Williams® have recently reported two experiments on 
the effects of feeding desiccated sheep thyroid containing different 
percentages of iodine to dogs. Of one preparation which contained 
0.0292 per cent iodine 11 grams fed to a dog in eighteen days did not 
cause a loss of weight, and the fresh thyroid of the dog on analysis 
yielded but 0.173 milligram iodine per gram. The second prepara- 
tion had 0.1092 per cent iodine. The dog which received 11 grams 
of this in eighteen days lost 454 grams weight and its fresh thyroid 
contained, per gram, 0.439 milligram iodine. 
These experiments, although very few in number and not of a 
character to admit of quantitative results, indicate clearly that there 
is a relation between the iodine content and the physiological activity 
of thyroid preparations. 
B. EXPERIMENTAL. 
METHODS. 
None of the methods discussed in the above review are suitable 
for a quantitative study of the physiological effects of different 
thyroid preparations. They are all time-consuming, and so do not 
admit of many experiments; furthermore, they are not adapted for 
showing small differences in activity. They did not suffice, for 
example, to demonstrate the physiological activity of thyroid free 
of iodine. It may also be mentioned that different animals and 
different patients may react differently to the same preparation; 6 
this has been observed both clinically and experimentally. If it 
were possible to test the various thyroid preparations upon the same 
individual fairly concordant results could probably be obtained, but 
such experiments are, as a rule, not feasible. 
Before beginning the description of the method which forms the 
basis of the experiments described in this bulletin a few words may 
be said in regard to some observations which we have made upon the 
relation between the activity of thyroid preparations and the loss 
in body weight which their ingestion may produce. Many of the 
results are given in the protocols of the experiments which follow, 
but in addition to these several experiments were performed expressly 
for determining whether a method based upon the loss in weight of 
the animals could be used for estimating the relative activity of 
a D. Marine and W. W. Williams, Archives of Internal Medicine, 1908, 1, p. 378. 
b The fact that there are such variations in the susceptibility of different individuals 
can not be considered an argument against the desirability of having thyroid prepara- 
tions of known strength. It is especially important that when the susceptibility of a 
patient to a given drug has been determined that treatment should be continued with 
a preparation of known strength — not with one half or three times as strong, as may 
readily occur with present commercial thyroid preparations. 
