20 
Ziegenbein® during 1901 and 1902 examined a number of speci- 
mens of digitalis leaves obtained from different localities estimating 
the digitoxin content and conducting comparative experiments by 
physiological methods. His results as given in the table on page 9 
show that no definite parallelism between the two can be found. 
The toxicity of the digitoxin, which he was able to isolate by the 
Keller or Keller-Fromme method, only accounted for about one- 
third of the activity of the leaves from which it was obtained. He 
examined the toxicity of the extract which was left after shaking it 
out with chloroform to remove the digitoxin, and found that some 
principles which were insoluble in chloroform still remained and 
accounted for another one-third of the activity of the leaves, but 
the remaining one-third could not be accounted for. He carried out 
some experiments to determine the effect of the fineness of the drug 
upon the toxicity of the infusion which when powdered gave a 
higher value than did infusions made from leaves which were simply 
cut up. The toxic dose for the former was found to be 0.048 gram, 
while the latter required 0.064 gram to produce the same -effect, and 
when finely powdered the leaves were most potent requiring only 
0.03 gram, the difference probably being due to the greater surface 
of the drug exposed to the solvent. The method he employed for 
the physiological estimations was that originated by Hans and 
Arthur Meyer. In this method, freshly caught male frogs (R. tem- 
poraria) were secured upon a board and the heart exposed in the 
usual manner. Definite amounts of the drug to be tested were then 
injected into the thigh lymph sac and the smallest amount was 
sought which would produce systolic standstill within two hours. The 
minim um lethal doses thus found were calculated upon the basis of 
100 grams frog weight in order to allow of comparisons. Frogs 
weighing about 25 grams were chosen for the experiments, but 
Ziegenbein did not think that a few grams difference in weight 
influences the results to any appreciable extent. He was also of the 
opinion that the season of the year makes very little difference in the 
susceptibility of frogs. 
In the following year Moschkowitsch b published a critical study 
of the method of standardizing digitalis preparations by means of 
their action on frogs. His experiments were carried out on R. 
temporaria, which were fastened to a board and the sternum re- 
moved to permit of free observation of the heart, the pericardium 
being left intact to prevent drying. The drug to be tested was 
introduced into a lymph sac and its activity was measured by the 
time when it first produced an effect on the heart and by the time 
necessary to cause systolic stoppage. 
a Ziegenbein, Arch. d. Pharmacie, 1902, CCXL, 454. Ber. d. Deut. Pharm. Gesells., 
1902, XII, 335. 
&H. F. Moschkowitsch, Arch. d. Pharm., 1903, CCXLI, 358. 
