THE ACTIONS OF PHYSOSTIGMA AND ATROPIA. 589 



Experiments with half the Minimum-Lethal Dose of Physostigma. — The con- 

 siderations which led me to anticipate that the counteracting influence of atropia 

 upon the lethal action of physostigma is successfully exerted only within a 

 definite range of doses, and that death may be produced when a lethal dose 

 of physostigma, which is capable of being rendered non-lethal by atropia, is 

 given in combination with a somewhat large non-lethal dose of atropia, also 

 led me to anticipate that death may be produced by the combined adminis- 

 tration of non-lethal doses of the two substances. Experiments were accord- 

 ingly made,* in which half the minimum-lethal dose of physostigma was adminis- 

 tered five minutes after various doses of atropia with the following results : — 



Experiment 58.— With 5 3 grains of sulphate of atropia, recovery occurred. 



Experiment 59. 

 Experiment 60. 

 Experiment 61. 

 Experiment 62. 

 Experiment 63. 

 Experiment 64. 

 Experiment 65. 

 Experiment 66. 

 Experiment 67. 

 Experiment 68. 

 Experiment 69. 

 Experiment 70. 



616 „ „ recovery 



6*2 „ „ recovery 



6 - 3 „ „ recovery 



6 - 5 „ „ recovery 



7* „ „ recovery 



8* „ „ recovery 



8 '8 „ „ recovery 



9* „ ,, recovery 



9*5 „ „ recovery 



9 - 8 „ „ death 



10* „ „ death 



105 ,, „ death 



It is shown by these experiments that when sulphate of atropia is adminis- 

 tered five minutes before half the minimum-lethal dose of physostigma, death 

 occurs if the dose of the former substance be nine grains and four-fifths, or more. 

 This result appears a very remarkable one, when it is considered that a very 

 decided counteraction is exerted by much smaller doses of atropia against the 

 poisonous action of doses of physostigma greatly in excess of the minimum- 

 lethal, and that the minimum-lethal dose of sulphate of atropia is about twenty- 

 one grains. It, however, merely confirms a legitimate anticipation when certain 

 of the results of the experiments with lethal doses of physostigma are borne in 

 mind. Actions essentially the same as those that are produced in excessive 

 amount when the administration of five grains and three-tenths of sulphate of 

 atropia along with the minimum-lethal dose of physostigma is followed by death, 

 also become excessive after the administration of nine grains and four-fifths 

 of sulphate of atropia along with half the minimum-lethal dose of physostigma. 

 The result may be simply explained by supposing some action or actions of 

 both physostigma and atropia wherein there is no mutual counteraction. 



* Tabular Summary, Series i. Table 1. 

 VOL. XXVI. PART III. 7 



