20 
thyroid preparations. The figures given in the protocols show the loss 
of weight for relatively short periods (ten to twenty days) and do 
not indicate that the method is of practical application. In the 
special experiments which were undertaken the animals (rats and 
guinea pigs) were fed during longer periods or until death occurred. 
The results showed that in general the thyroid with the largest per- 
centage of iodine produced death earliest, but in no case was more 
than a rough quantitative application of the data possible. It is 
probable that the primary effect of thyroid feeding is the same in 
different animals, but that other factors, such as appetite, rate of 
excretion, etc., which can not be controlled, are involved, and these 
determine the final result. 
The method which we have developed for comparing the physiolog- 
ical activity of different thyroid preparations has for its basis the 
effect of thyroid feeding upon the resistance of animals to certain 
poisons. Having found that the administration of thyroid alters 
the resistance of animals to certain poisons, we performed .a large 
number of experiments in order to determine which poisons were 
most suitable for comparative studies. The principal poisons tested 
on mice are included in the following list, and in most cases, as will 
be seen, negative results were obtained. With many of the compounds 
in the list but two or three experiments were performed; hence we 
can not state positively that the feeding of thyroid in these cases 
had no effect upon the resistance to the substance in question. The 
thyroid, in amounts varying from 0.001 to 0.1 gram per day, was 
fed in the form of cakes; the poisons were injected subcutaneously: 
Acetonecyanhydrine 
Acetonitrile 
Acetylmorphine (‘ ‘ Heroin ”). . . 
Antipyrine 
Atropine 
Benzonitrile 
Butylcarbylamine (tertiary) . . . 
Caffeine 
Capronitrile 
Chloral hydrate 
Codeine 
Ethylcarbylamine 
Ethylenecyanide 
Guanidine carbonate 
Guanidine sulphocyanate 
Hydrocyanic acid 
Isovaleraldehydecyanhydrine . . 
Methylamine 
Methylethylketonecyanhydrine. 
Morphine 
Nicotine 
Resistance slightly increased (?). 
Resistance much increased. 
Resistance diminished. 
No effect. 
No effect. 
No effect. 
No effect. 
No effect. 
No effect. 
Resistance diminished(?). 
Resistance diminished . 
No effect. 
Resistance increased. 
No effect. 
No effect. 
No effect. 
No effect. 
No effect. 
No effect. 
Resistance diminished. 
No effect. 
