598 DR THOMAS R. FRASER ON THE ANTAGONISM BETWEEN 



Experiment 163. — With 5* grains of sulphate of atropia, recovery occurred. 

 Experiment 164. ' „ 7: „ „ recovery „ 



Experiment 165. „ 7'5 „ „ recovery „ 



Experiment 166. „ 8* ,, „ death „ 



Experiment 167. „ 816 „ „ death „ 



The smallest quantity 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 is thus shown to be about eight grains per three pounds 

 weight of rabbit. In the analogous experiments of the first series a similar result 

 was obtained, for although there death did not occur unless the dose of atropia 

 was at least nine grains and four fifths, it is probable that this comparatively 

 slight difference may be due to the physostigma having been given in that series 

 in the form of extract. It will be remembered that the minimum-lethal dose 

 of sulphate of physostigmia is somewhat less than one-tenth of that of extract 

 of physostigma. For convenience of comparison, however, it has been assumed 

 in the second series of experiments, that sulphate of physostigmia is exactly ten 

 times as active as extract of physostigma. 



With these experiments, the second series is completed. I have not con- 

 sidered it necessary to construct a diagram of the entire series, as all its special 

 characters are displayed in the diagrams representing the experiments in which 

 the doses of physostigma were lethal. With less than lethal doses, the results 

 are so similar to those of the first series of experiments that the region of 

 recovery would be of essentially the same form as that represented in 

 Diagram 5. 



III. Determination of the Influence of the interval of Time between the 

 Administration of the two substances, upon the Dose of Atropia 

 required to counteract a given dose of physostigma. 



In the two series of experiments that have already been described, the two 

 following series of dose-limits of successful antagonism have been determined, 

 namely, those limits where the atropia is given five minutes before, and those 

 where it is given five minutes after the physostigma. Further, it has been shown 

 that the limits in the one series differ somewhat from those in the other ; and 

 when this result is taken in connection with several obvious considerations, it 

 is evident that the series of close-limits of successful antagonism will be different 

 for every different time-relation in the administration of the two substances. 

 It is, however, evident that to make for each of any considerable number of 

 other time-relations in the administration of the two substances, a complete 

 series of experiments on the plan of the two series already described, would 

 entail an amount of labour quite out of keeping with the value of any results 



