CYCLIC ACTIVITIES OF LIFE 249 



utmost delicacy ; it is only within fairly 

 close limits that the rapid to and fro swing is 

 possible. Appreciable variation in any one 

 of these factors, or the presence of traces 

 only of various drugs such as chloroform, or 

 various cardiac tonics, soon slow or hasten 

 the beat, and a little additional excess (or 

 defect of the normal constituents) stills the 

 organ completely, or sends it into delirium 

 also ending in stoppage. 



Other more slowly oscillating living systems 

 allow greater variations, but each has its 

 limits which must not be surpassed. Fatigue 

 after daily work and the nightly recuperation 

 in sleep are examples of the effects of slower 

 accumulation of waste products. The elimi- 

 nation of these fatigue products, and the 

 building up of fresh reserve stores within the 

 cells during sleep complete the cycle. 



Phasic or rhythmic activity in some degree 

 or other, and with widely varying rates, 

 is inherent in the various crystallo-colloids 

 of all living matter. It is seen in the un- 

 striated, or involuntary, muscle of all parts 

 of the body, such as alimentary canal, bladder, 

 uterus, spleen, arterial walls, everywhere 

 with varying rhythm in different situations, 

 according to development and requisite 

 physiological functions. It is seen in all the 



