590 DR. THOMAS R. FRASER ON THE ANTAGONISM BETWEEN 



The effects that are produced by a combination of half the minimum-lethal 

 dose of physostigma with sufficiently varied doses of atropia being thus 

 determined, the entire regions of recovery and of death in the series of experi- 

 ments in which atropia was administered five minutes before physostigma may 

 now be considered. 



This series is completely represented in Diagram 5 (Plate XXIV.), which 

 has been constructed on the same plan as Diagram 1, from which, however, it 

 differs in so far that the increase in the doses of atropia, represented by the 

 distance in a horizontal direction from the perpendicular line forming the left 

 margin of the diagram, proceeds at the rate of one-tenth of a grain for every 

 subdivision of the horizontal lines, in place of for every two subdivisions. This 

 modification was required to curtail the lateral extension of the diagram, so as 

 to retain it within convenient limits. 



The area covered by the diagram includes every possible close of physo- 

 stigma from the minutest fraction of the minimum-lethal dose to one four 

 times as large as the minimum-lethal, and every possible dose of atropia below 

 the minimum-lethal. In the previous section of this paper, a series of experi- 

 ments was described which rendered it probable that the minimum-lethal dose of 

 atropia for rabbits is about twenty-one grains for every three pounds weight 

 of animal ; and I have specially indicated the position of this dose by a red 

 perpendicular line, which will be seen near the right margin of the diagram. 



In the diagram, the region of recovery (pink) appears to be a very 

 restricted one when contrasted with the region of death (blue); and it is 

 almost unnecessary to point out that this relation may be greatly exaggerated 

 by enlarging the diagram so as to include within it a portion of the almost 

 unlimited area in which death occurs after combinations of physostigma and 

 atropia unrepresented in the present diagram. As the region of recovery after 

 lethal doses of physostigma occupies only that portion of the pink space which 

 extends above the red horizontal line, the area that it occupies appears almost 

 insignificantly small. Seeing, however, that a dose of physostigma three mid 

 a half times as large as the minimum-lethal is included within this region, its 

 insignificance in relation to the entire region of death becomes of but little 

 importance, when the interesting fact of the counteraction of so enormous a 

 dose is realised. 



The diagram very clearly displays the singular result, that death may follow 

 the administration of physostigma and atropia in doses both below the mini- 

 mum-lethal. The combinations that are able to produce this result are included 

 within the blue space below the red horizontal line. The direction of the 

 line separating this space from the subjacent area of recovery (pink) is 

 much more horizontal than that of the line separating the region of death from 

 that of recovery after lethal doses of physostigma. The change of direction 



