THE ACTIONS OF PHYSOSTIGMA AND ATROPIA. 599 



that might fairly be looked for. The most interesting of such results would be 

 the determination for each case of given doses of the two substances compatible 

 with the production of successful antagonism of the maximum period separat- 

 ing the administration of the one substance from that of the other, both when 

 the atropia is administered before, and when it is administered after the physo- 

 stigma. 



In the experiments of the present series (3d), I have contented myself with 

 determining this period in the case of one constant dose of physostigma with 

 doses of atropia ranging from the one-hundredth of a grain to five grains. 

 When the results derived from this series of experiments are considered along 

 with those of the first and second series, an indication will, I believe, be obtained 

 of the limits in the period separating the administration of the two substances 

 within which successful antagonism may occur, even for the cases where the 

 combination of doses of physostigma and atropia is different from any combina- 

 tion included in the present series. 



The dose of physostigma I have selected for these experiments is one 

 equivalent to one and a half times the minimum-lethal dose; and it was 

 administered in the form of sulphate of the active principle, of which prepara- 

 tion this dose is represented by three twenty-fifths of a grain per three pounds 

 weight of rabbit. With each dose of atropia that was given in combination 

 with this dose of physostigma, several experiments were made, which differed 

 from each other by a difference in the interval of time separating the adminis- 

 tration of the two substances; this interval being in the first experiments 

 such as to permit of successful antagonism, and being in each subsequent ex- 

 periment altered until at length it became such as no longer to permit of suc- 

 cessful antagonism. This, at least, was the general plan followed in this series, 

 but it was somewhat departed from on several occasions, when the circum- 

 stances of the experiments prevented or rendered inconvenient its adoption. 

 Briefly stated, the distinguishing characters of the series were that the dose of 

 physostigma was constant, while the dose of atropia and the interval of time 

 between the administration of the two substances varied. 



In certain of the experiments atropia was administered before physostigma, 

 and in others physostigma before atropia; and in order to connect together 

 these two groups of experiments, a third group was undertaken in which atropia 

 and physostigma were administered as nearly simultaneously as possible. In 

 describing the chief results, I shall, as a matter of convenience, in the first place 

 consider (a) the experiments in which the two substances were simultane- 

 ously administered ; then (b) the experiments in which atropia was administered 

 after physostigma; and finally (c), the experiments in which atropia was 

 administered before physostigma. 



(a) Experiments in which Atropia and Physostigma were administered 



