154 THEORY OF INJURY AND RECOVERY 



which is reached as the result of recovery gets lower. This is pre- 

 cisely what happens in the experiments with NaCl. It would there- 

 fore appear as though the same mechanism of recovery were involved. 

 If this is so the same method of calculation should enable us to pre- 

 dict recovery in both cases. This is found to be true. Using the 

 same formulas which have already been employed in the experiments 

 with NaCl we are able to predict the course of the curves obtained 

 in experiments with CaCl2. This is rather striking in view of the 

 fact that the two sets of curves differ so fundamentally in appearance. 



In calculating the curves for CaCl2 the constants given in Table I 

 are employed. The results are shown as unbroken lines in Fig. 2 

 (the dotted lines show the experimental results). It is evident that 

 the agreement is very satisfactory. 



Some assistance in picturing the reactions which occur during expos- 

 ure is afforded by Fig. 3, which shows the curve of in NaCl (unbroken 

 line) and in CaClo (dotted line). These curves are plotted from the 

 calculated values; the observed values are shown as points; it will be 

 observed that they lie fairly close to the calculated curve. The figure 

 also shows the calculated values of 5: in this case no observed values 

 are given because such values cannot be very precisely determined. 

 This is owing to the fact that the value of S affects only the speed of 

 recovery (not the final level attained) and as the speed is variable 

 the only satisfactory procedure is to assume such values of iv^ and 

 Ks as cause the closest approximation to the observed speed of 

 recovery. When these values have been found the value of 5 can 

 readily be calculated. The results of these calculations are plotted 

 in Fig. 3. 



In this figure the ordinates give the values of O: these must be 

 multiplied by 6.75 to obtain the values of S. In all curves the value 

 of kS at the start is 2.7 (the value of 5 in sea water^^) ; this appears on 

 the ordinate in the figure as 2.7 -^ 6.75 = 0.4. The curves rise to a 

 maximum and then fall to zero. The curves for start at 100 and 

 fall to 10 (since the base line is taken as 10, just as in the curve of M). 



^^ The normal value of S in sea water is taken as 2.7 which is exceedingly small 

 as compared with the amount of 0. The amount of S which is produced from 

 in each unit of time is relatively large but 5 is so rapidly transferred into A that 

 its amount in sea water never becomes greater than 2.7. 



