470 Prof. J. T. Cash and Dr. W. R. Dunstan. [May 24, 
sequence of ventricular upon auricular action, with a resulting rise in the 
pressure being observed on stimulating during the stage of cardiac irregu- 
larity. The proportion of indaconitine capable of producing such results was 
00011 gramme per kilogramme and upwards, administered hypodermically 
in a single dose. When one-half of the lethal proportion (per kilogramme) 
was repeated at intervals of 45’, the third dose was followed in rabbits by 
great irregularity of the pulse, wide fluctuations in blood-pressure, and rapid 
decline in respiratory frequency. The long inspiratory pause, with the forced 
effort at its commencement, became more marked as the toxic action 
progressed. This proportionate dose repeated twice at intervals of 45’ may 
prove lethal, though this is an exceptional occurrence. 
No estimation was made of the lethal dose of indaconitine for non- 
anzsthetised cats, but taking the proportion as 0:00012 which is applicable 
to rabbits, it was found that half this dose, administered hypodermically and 
repeated every 45’, was followed by death in etherised cats about 70’ after 
the third injection. The effects were thus developed :— 
After First Lnjection—Acceleration (transitory) and slowing of the pulse. 
Moderate fall of arterial pressure. Slight acceleration followed by slowing of 
the respiration. 
After Second Injection—Continued slowing of the pulse. Thereafter 
acceleration. Blood-pressure fairly steady. Further slowing of the respira- 
tion. Usual results of peripheral vagus and splanchnic stimulation. 
After Third Inyection.—Irregularity of the pulse increasing as time pro- 
gressed. The heart greatly accelerated, attaining 200 per minute. Imme- 
diately before death, and when the blood-pressure amounted to 28 mm. of 
mercury, the rhythm became regular. In the earlier part of this period, vagus 
stimulation co-ordinated the action of the auricles and ventricles, temporarily 
raising the blood pressure, but this effect was lost later. Splanchnic 
reaction was never entirely abolished. The respiration, at first very slow but 
effective, became weaker and was suspended. Artificial respiration served to 
prolong life for over 20’. The tracings (Ai—3) are taken from an experiment 
in which registration of carotid pressure and contraction of the left auricle 
and ventricle were taken simultaneously. 
A. Before injection. 
A». 50’ after the third injuction of 0°5 lethal dose of indaconitine. (The 
injections occur every 45’.) 
A3. 70’ after the third injection, and 5’ before death. 
