CHAP, in.] THE PHASKS OF LIFE. 1157 



and fall of activity in the vaso-motor centres. And lastly, 

 there stands out the fundamental fact of all bodily periodicity, 

 that alternation of the heart's systole and diastole which ceases 

 only at death. Though, as we have seen, the intermittent flow 

 in the arteries is toned down in the capillaries to an apparently 

 continuous flow, still the constantly repeated cycle of the cardiac 

 shuttle must leave its mark throughout the whole web of the 

 body's life. Our means of investigation are, however, still too 

 gross to permit us to track out its influence. 



