THE ACTIONS OP PHYSOSTIGMA AND ATEOPIA. 597 



dose of atropia capable of preventing death after the minimum-lethal dose of 

 physostigma and the smallest capable of doing so after a close three and a half 

 times as large is only nine one-hunclreclths of a grain, whereas the difference 

 between the largest closes is so great as five grains. When atropia is given 

 five minutes after physostigma, the difference between the smallest dose capable 

 of preventing death after the minimum-lethal dose of physostigma and after a 

 dose three times as large is only thirteen one-hunclredths of a grain, whereas 

 the difference between the largest doses is so great as two grains and nine 

 twentieths. 



In order more clearly to display the differences between a b in the two series 

 of experiments, I have drawn other two diagrams, in which the irregularities of 

 this line are more distinctly shown than in Diagrams 1 and 3. This has been 

 effected by simply diminishing the value of the subdivisions of the horizontal 

 lines, so that each tenth of a grain of sulphate of atropia is indicated by twenty 

 subdivisions in place of by two. By this modification, the direction of the line 

 a b has been rendered less perpendicular, and at the same time its course has 

 been more accurately defined. Diagram 2 represents the experiments of the 

 first series, and Diagram 4 those of the second, and only so much of each series 

 has been included as is required to exhibit the course of a b. It will be seen 

 that in Diagram 4 the line a b is more irregular in its course than in Diagram 2, 

 and that in Diagram 2 a number of irregularities are displayed in this line, which 

 are not apparent in Diagram 1, where the same series of experiments is repre- 

 sented in a more contracted form. 



It will likewise be seen from an inspection of the diagrams illustrative of 

 these two series of experiments, that in rabbits a dose of sulphate of atropia 

 equivalent to four twenty-fifths of a grain per three pounds- weight of animal is 

 able to prevent the fatal effect of any quantity of physostigma which can be 

 rendered non-fatal by atropia, and that even a very slight modification of this 

 dose suffices to curtail the extent of successful antagonism. There can be 

 little doubt that in every species of animal some dose of atropia occupies a 

 similarly important position, and bears a similar relation to the range of suc- 

 cessfully counteracting doses. A result of some practical value has probably 

 been obtained by the establishment of the fact that this dose is much nearer 

 the minimum than the maximum in the range of the doses of atropia capable 

 of preventing the lethal effect of physostigma. 



Experiments with half the minimum-lethal dose of physostigma. — The next 

 experiments were made in order to determine the smallest dose of atropia that 

 in conjunction with half the minimum-lethal dose of physostigma administered 

 five minutes before it is sufficient for the production of death/"" The following 

 results were obtained : — 



* Tabular Summary, Series ii. Table 1. 

 VOL. XXVI. PART III. 7 Q 



