CIRCULATION. 101 



as follows, taking one complete rotation of the 



drum for each variation: 



(#) Slow initial contraction of bulb and slow re- 

 laxation 



(^) Slow initial contraction of bulb and quick re- 

 laxation. 



(V) Quick initial contraction of bulb and slow re- 

 laxation. 



(</) Quick initial contraction of bulb and quick 

 relaxation. 



(e) Same as d with slow rhythm. 



(/) Same as d with rapid rhythm. 



(3) Make a careful study of these tracings and deter- 

 mine : 



(#) The characteristic and essential features. 



(/) The accidental and nonessential features. 



(V) The cause of the essential ? 



(</ The cause of the nonessential features? 



