CYCLIC MOLECULAR VARIATION 643 



The two halves of the cycle are thus strangely alike, one 

 being, as it were, a reflection of the other. The cycle begins 

 with sub-tonicity, due to a deficit of absorbed stimulus, and 

 ends with the abnormality caused by excess of stimulation. 

 The starting-point of the one may be supposed to meet the 

 end of the other in a common fatality. The tissue comes to 

 the same death by inanition on the one hand, through lack 

 of stimulation, and by fatigue, on the other, through over- 

 stimulation. But though the one half thus mimicks the other, 

 there is, as it were, a polar difference between the two, by 

 reason of the difference in their past histories. To revive the 

 dying tissue, in the beginning of the cycle, stimulation is 

 necessary ; to revive it afresh, at the termination of the cycle, 

 a period of rest is essential. 



T T 2 



