51 
DISCUSSION OF METHODS OF ASSAY. 
A superficial examination of the tables giving the summary of the 
results obtained would seem to indicate the practical worthlessness 
of the biological assay of digitalis preparations by the methods now 
in vogue. This is especially emphasized by a comparison of Digitol 
and the Concentrated tincture made by Burroughs, Wellcome & Co. 
These give comparative values as follows: 
Mice, 
toxic dose. 
Guinea 
pigs. 
toxic dose. 
Frogs, 
one hour. 
Digitol No. 1 
Concentrated tincture 
mgm. 
4.0 
4.0 
mgm. 
0.70 
. 35 
c. c. 
0. 012 
.020 
Here are two preparations which according to' the first test are of 
the same strength; by a second test one is half the strength of the 
other, and by a third method exactly the reverse relation is found. 
No explanation can be suggested for the results obtained on mice 
and guinea pigs; there was no possibility of a mistake, as the results 
were confirmed on numerous animals as the tables show, and with 
different solutions made up on different days. A closer examination 
of the table shows that these results are certainly exceptional, the 
vast majority being more uniform, as, for example, the two prepara- 
tions named are shown by most of the methods to be the strongest 
of any of the specimens examined. Also comparing the four U. S. 
Pharmacopoeia fluid extracts made byHance Brothers & White, Parke, 
Davis & Co., Nelson, Baker & Co., and Sharpe & Dohme, these were 
found by several of the methods to be of very nearly the same strength, 
differing not more than 25 per cent. Also the Digitalone prepara- 
tions and Lloyd’s Specific Medicine appear at the bottom of the list 
in almost every table showing by every method their comparative 
weakness. 
There appears thus to be some slight uniformity in the results 
obtained by the different methods. This is indeed far from close, 
but this fact is not surprising when the factors concerned in the 
different methods of assay are considered. In the first place it 
could hardly be expected that animals differing so widely as cats and 
frogs, mice and guinea pigs would react exactly alike to the different 
preparations. The cause of death is not the same in the mice and 
guinea pigs as in the frogs and the cats under the conditions of our 
experiments. With frogs the action is always one upon the heart; 
also in the cats we maintained artificial respiration so that the figures 
obtained there indicate a cardiac action. On both mice and guinea 
pigs, however, the cause of death in probably every case is not due 
