456 



Characteristics of the Ampullar Pulsations. 



Tahle 4 gives the average times of the systole and diastole in 9 

 series of observations, each continued, on an average, for 17 seconds. 

 It shows that the contraction is very slow, much slower than the con- 

 tractions of the zoöids and hearts which are accomplished by means 

 of muscles. The systole is usually decidedly longer than the diastole» 

 but the two exceptions, series 5 and 9, seem to show that the time 

 relations are easily modified. Thus in series 4 the pulsations had the 

 usual characters, but in less than one hour (series 5) they had changed 

 so much that the average time of the diastole had increased from 32 

 to 42 seconds. As the ampullae remained the same it would seem 



Table 4. 



that this change was due to variation in the conditions external to the 

 ampullae, such as the distribution and pressure of the blood. In series 

 8 and 9, however, adjacent ampullae were observed at the same time, 

 and, as the external conditions must have been nearly the same, the 

 differences in the pulsations must be explained by differences within 

 the ampullae. It must be concluded then that the lengths of systole 

 and diastole are determined both by influences from without and within 

 the ampullae. 



Of the external influences that may act upon the ampullae blood 

 pressure has already been mentioned. Several methods were tried to 

 ascertain whether a slight increase in the blood pressure would leng- 



