THE ACTIONS OF PHYSOSTIGMA AND ATROPIA. 



615 



perpendicular sections parallel to and on either side of b b' and a a', and of 

 horizontal sections parallel to and below and above c a V b a d. To obtain a 



,.?T(i 



Diagram 7. 



This woodcut is an orthogonal projection of a model in which the curves separating the regions 

 of recovery and death in the three series of experiments are brought into proper relationship to each 

 other. The curve of the first series of experiments is represented by a a, that of the second series by 

 b b', and that of the third series by c a' b' b a d. Doses of physostigma are indicated by the distance 

 (parallel to the axis of z) from the plane Y O X ; doses of atropia, by the distance (parallel to the axis 

 of x) from the plane ZOY; and intervals of time between the administration of the two substances, by 

 the distance (parallel to the axis of y) from the plane Z X, points on the Y side of this plane indi- 

 cating atropia administered before physostigma, and points on the Y' side indicating atropia administered 

 after physostigma. The curve c a b' b a d intersects the curve a a at a and a, and the curve b V at 

 b' and b ; the points a and a indicating the positions respectively of the largest and the smallest doses 

 of sulphate of atropia that produce successful antagonism when administered five minutes before one 

 and a-half times the minimum-lethal dose of physostigma, and the points b' b the positions respectively 

 of the largest and smallest doses of sulphate of atropia that produce successful antagonism when 

 administered five minutes after this dose of physostigma. 



In this diagram, the line cab' b ad has been drawn without taking into account the apparently ano- 

 malous experiments already discussed in page 602. The interrupted line c d occupies the supposed posi- 

 tion of a line that would represent the results of a series of experiments in which a fixed dose of 

 sulphate of atropia (5 grains per three pounds weight of animal), and varying doses of physostigma 

 were administered at varying intervals of time. Such a series of experiments has not been made, 

 but the points of intersection of this line with the lines b b', a a', and c a b' b a d are fixed by the 

 position of the latter lines. 



I am indebted to my friend Professor Crum Brown for the drawing from which this woodcut has 

 been made, as well as for many valuable suggestions relative to the preparation of the other diagrams 

 in this paper. 



