510 
Proceedings of the Royal Society 
would show that fatal experiments occur in this region, not only 
with fatal closes of atropia given in combination with less than 
fatal doses of physostigma, but also with less than fatal doses 
of atropia given in combination with less than fatal doses of 
physostigma. 
In this manner, the entire superficial area of the region of suc¬ 
cessful antagonism has been defined, when physostigma is given 
five minutes after and five minutes before atropia. In addi¬ 
tion to this, what may he termed the thickness of the region 
has been determined. For this purpose, series of experiments 
were made, in each of which the doses of physostigma w T ere the 
same, and the doses of atropia varied ; while with each dose of 
atropia, several experiments were made which differed from each 
other by a difference in the interval of time between the adminis¬ 
tration of the two substances. From the data thus obtained, curves 
have been constructed; the dose of physostigma serving as the 
base-line, the various doses of atropia as the abscissas, and the dif¬ 
ferent intervals of time that separate successful from unsuccessful 
experiments as the summits of the ordinates. When these curves 
are brought into relation with a diagram of the superficial area of 
the region of successful antagonism, in such a manner that the 
base-lines, representing the doses of physostigma, correspond to 
each other, and that the ordinates of these curves extend at right 
angles to those in the diagram of the superficial area, the lateral 
extension of the region of successful antagonism may be defined. 
In this way, its lateral as well as its superficial extent has been 
indicated with atropia and physostigma. 
After defining the superficial area and the thickness of the 
region of successful antagonism, it seemed of interest to ascertain 
what dose of atropia is required to produce death with a dose of 
physostigma below the minimum fatal. The experiments per¬ 
formed for this purpose show that when one-half of the minimum 
fatal dose of physostigma is given five minutes after atropia, so 
large a dose of the latter substance as 9‘8 grains is required in 
order to cause death; recovery taking place with doses ranging 
from 3 to 9’5 grains. 
The minimum fatal dose of sulphate of atropia given alone was 
found to be twenty-one grains for a rabbit weighing three pounds. 
