DIVERSE COMPONENTS 



351 



may be studied either in situ or isolated. The examples here chosen 

 give preference to "non-chemical" components. 



In man, heart frequency is perhaps the physiological quantity 

 most often measured. Enormous numbers of circumstances are 

 loosely known to disturb it ; yet the quantitative tolerance curves 

 describing its modifications are few except in physical exercise. 



Recoveries occur in very short periods of time ; therefore data 

 are selected in which frequencies are counted in intervals of 0.3 

 minutes. Choosing recovery from physical exercise and from 

 depressor stimulation (fig. 175), I relate the decelerations and 

 accelerations of heart beat to the increments in frequencies (loads) 



■4000i 



3000 



•ZOOQ 



o 



'1000^ 



80 



►100 +IZO 



*20 +40 -GO 



ct Load Hear-fc Frec^uency 



Pig. 175. Acceleration and deceleration of heart beat in relation to mean frequency 

 of beat. Man. Decelerations are computed as decreases of frequency during the first 

 0.005 hour (18 to 20 seconds) of recovery at the completion of physical exercise (run- 

 ning). Accelerations are during the first 20 seconds after release of pressure on the 

 region of the carotid sinus. Increments and rates of change are all in per cent of the 

 resting frequencies that prevailed before exercise or compression began. Squares, 2 

 hypertensive individuals of Mies ('32). Triangles, 4 groups of 8 to 12 tests each in 

 12 individuals; data of Cotton and Dill ('35). Circles, 4 groups of 11 to 15 tests each 

 on 26 individuals; 11 of whom were trained runners; data of Dill and Brouha ('37, 

 pp. 13 to 16). 



during those initial intervals. A net equilibration diagram 

 results. 



As was done for other components, those who made the observa- 

 tions presented the data as found under conditions named, without 

 stopping to test what nerves or endocrine organs could be blocked 

 without interfering in the recovery. Possibly faster recoveries will 

 be found under some other conditions ; and it can always be sup- 

 posed that recovery for the heart begins at some time other than 

 at the cessation of leg-running or at the release of pressure on the 

 neck. 



