508 Proceedings of the Royal Society 
vent death after the administration of different fatal doses of 
physostigma, and the maximum fatal dose of physostigma that is 
capable of being rendered non-fatal by atropia were ascertained, and 
it was found that beyond these various points death may be pro¬ 
duced by combined doses of the two substances, either by some 
non-antagonised action belonging to one or other of them, or by a 
combination of similar actions belonging to both. 
As the above results could be obtained only by performing 
a very large number of experiments, rabbits were the animals 
selected, it being impossible to obtain a sufficient number of dogs, 
or other convenient animal. The weight of animal employed was, 
as nearly as possible, three pounds; and when below or in excess 
of this a correction was made, so that each dose represented three 
pounds weight of animal. 
In one portion of this investigation, experiments were performed 
in which physostigma was given five minutes after atropia, both 
substances being injected under the skin. In the first series, the 
dose of physostigma was the minimum fatal, and the doses of 
atropia ranged from one that was too small to prevent the lethal 
action of this dose of physostigma, through a number of gradually 
increasing doses of atropia that were able to prevent death, until a 
dose was found whose administration resulted in death. Similar 
series of experiments were made with doses of physostigma one and 
a-half times, twice, two and a-half times, thrice, and three and 
a-half times as large as the minimum fatal. With the minimum 
fatal dose of physostigma, it was found that while ‘01 grain of 
atropia is too small to prevent death, ’015 grain is able to do so; 
and that with any dose ranging from *015 grain to 5'2 grains the 
lethal effect of this dose of physostigma may be prevented; while 
if the dose of atropia be 5’3 grains or more, the region of successful 
antagonism is left, and death occurs. With one and a-half times 
the minimum fatal dose of physostigma, successful antagonism was 
produced with doses of atropia ranging from -02 grain to 42 
grainswith twice the minimum fatal of physostigma, wfith doses 
of atropia ranging from 025 grain to 3'2 grains; with two and a- 
half times the minimum fatal of physostigma, with doses of atropia 
ranging from *035 grains to 2'2 grains; with thrice the minimum 
fatal of physostigma, with doses of atropia ranging from -06 grain 
