THE ACTIONS OF PHYSOSTIGMA AND ATROPIA. 587 



It has occasionally happened, especially when the subject of the experiment 

 was a young animal, that the atropia effects were unusually slight. If the 

 description in the Tabular Summary of Experiment 152 be compared with that 

 of other experiments in which the same relative dose of atropia was ad- 

 ministered, it will be observed that the action of atropia was not developed 

 with its usual prominence, and that, consequently, the physostigma action was 

 only feebly counteracted. 



Experiments with Four times the Minimum-Lethal Dose of Physostigma. — 

 When atropia was administered five minutes before a dose of physostigma 

 equivalent to four times the minimum-lethal dose, the following results were 

 obtained: — * 



Experiment 158. — With 01 grain of sulphate of atropia, death occurred. 

 Experiment 159. ,,015 „ „ death ,, 



Experiment 160. „ 2 „ „ death „ 



Experiment 161. „ - 2 „ ,, death „ 



Experiment 162. „ 0-3 „ ,, death „ 



It was unnecessary to proceed further with these experiments, as it had been 

 rendered obvious by those previously made, that the lethal action of this large 

 dose of physostigma cannot be prevented by atropia, if a dose of this substance 

 between one-tenth and one-fifth of a grain be unable to do so. 



It has, accordingly, been shown that the maximum dose of physostigma 

 which can be rendered non-fatal by atropia administered five minutes pre- 

 viously is three and a half times the minimum-lethal dose. It has also been 

 shown that the range of doses of atropia capable of preventing death after the 

 administration of lethal doses of physostigma diminishes as the quantity of 

 physostigma increases. 



When these experiments are represented in a diagrammatic form, the results 

 that have been obtained may be clearly and readily appreciated. A simple 

 plan on which to construct a diagram is obviously suggested by the arrange- 

 ment that has been followed in the description of the experiments. By placing 

 symbolic representations of the results of the experiments performed with 

 each lethal dose of physostigma in horizontal lines, and by arranging these 

 lines so that the doses of physostigma shall succeed each other in regular 

 sequence and at proper intervals, we may obtain a picture which graphically 

 represents the various results that have been mentioned. 



Diagram 1 (Plate XXIII.) illustrates the experiments described above, in 

 which atropia was administered five minutes before lethal doses of physostigma. 

 The experiments that terminated in death are represented by crosses, and those 



* Tabular Summary, Series 1, Table 8. 



