THE PROBLEM AND METHODS OF INVESTIGATION 81 



one-half hours. Essentially the same differences appear in 4 per 

 cent alcohol, in 2 per cent ether, and in solutions of various other 

 depressing agents. 



These data may be presented more clearly and briefly in graphic 

 form, as in Fig. 3, which is a graphic presentation of Table I. In 

 Fig. 3 the curve ab is the death curve or susceptibility curve of the 

 ten young worms of Lot i, the curve cd the susceptibility curve 

 of the ten old worms of Lot 2. 1 Each curve is a descending curve: 

 the distance of its starting-point (a, c, Fig. 3) to the right of the 

 vertical line, the axis of ordinates, indicates the length of time 

 between placing the animals in cyanide and the beginning of death 

 and disintegration; its slope indicates the average rate of disinte- 

 gration; the distance of its lower end (&, d, Fig. 3) from the axis 

 of ordinates indicates the length of time between placing the animals 



1 The transformation of the tabulated data into graphic form is accomplished 

 by giving a numerical value to each stage of disintegration and determining the average 

 stage of disintegration in any lot at any given time by multiplying the number of worms 

 in each stage at that time by the value of that stage, adding the products for all stages, 

 and dividing by ten. By marking off vertical intervals from above downward, cor- 

 responding to the numerical values assigned to the different stages, as in Fig. 3, the 

 average stage of disintegration can be plotted at once by counting downward from 

 the zero point the number of spaces equal to its numerical value, or, in other words, 

 the ordinate of the susceptibility curve for any average stage of disintegration is equal 

 to 40 minus the value of that stage. 



The determination of the average stages of disintegration and of the disintegra- 

 tion ordinates for the time i . 30 in Table I will serve to illustrate the method of pro- 

 cedure. The values assigned to the different stages are: Stage I, o; Stage II, 10; 

 Stage III, 20; Stage IV, 30; Stage V, 40. 



Condition of Lot i : 2 animals in Stage III: 2X20= 40 



3 " " " IV: 3X30= 90 Average 



Stage of 



5 V: 5X40 = 200 Disinte- 



gration 



Condition of Lot 2 : 8 " " " I: 8X0= o 



2 " " " II: 2X10= 20 



2O-MO= 2 



Ordinate for Lot i at i| hours =40 33= 7 



Ordinate " " 2 " " " =40-2 = 38 



The horizontal distances of the points of the curve from the zero point at the left 

 (abscissae) in Fig. 3 represent lengths of time in the cyanide, half-hour intervals, 

 the intervals at which the condition of the animals was recorded being indicated on 

 the axis of abscissae. 



