138 The Philippine Journal of Science 1916 



We endeavored to reduce to a minimum all factors that might 

 affect blood pressure, such as emotions, excitement, ingestion of 

 food, exercise, and contractions of the muscles under the cuff, 

 by explaining to each subject the object of the work, by giving 

 him at least five minutes rest before his blood pressure was 

 taken, and by making these determinations in the majority of 

 cases in the hours between meals — ^that is, between 9 and 11 

 o'clock in the morning. 



In all of our observations a cuff 10.5 centimeters wide was 

 used with the exception of the first sixty cases, in which a 12.5- 

 centimeter cuff was employed. By comparing the readings taken 

 with the two cuffs, we found an average difference of 2.4 milli- 

 meters in the systolic reading and 0.8 millimeter in the diastolic. 

 In all the tables that follow, the readings have all been reduced 

 to the basis of the 12.5-centimeter armlet. 



CRITERIA USED IN READING SYSTOLIC AND DIASTOLIC BLOOD 



PRESSURE 



The criteria we used in reading the systolic pressure are the 

 same as those used by Erlanger, (7) as follows: a, a marked 

 increase in the amplitude of the pulsation traced on the revolv- 

 ing drum (Plate II, fig. 2) ; b, a change in the direction in the 

 trough line (Plate II, fig. 1) ; c, a marked separation of the 

 limbs of the pulse wave (Plate II, fig. 1). 



The criterion used in determining diastolic pressure is the 

 marked decrease in amplitude in the oscillations (Plate II, fig. 2) . 



In determining systolic pressure, we gave more attention to 

 criteria a and c and least attention to criterion b. 



DIFFICULTIES MET IN THE METHOD USED IN READING THE SYSTOLIC 



PRESSURE 



In reading our records, we often met such difficulties as the 

 noncoincidence of the two criteria, that is, when the marked 

 increase in amplitude of the oscillation is not coincident with 

 the marked separation of the limbs of the pulse wave (Plate II, 

 fig. 3, and Plate III, fig. 1). In these cases we generally base 

 our reading on the criterion that appears first. 



In a few cases criteria a and c appeared, disappeared, then 

 appeared again (Plate III, fig. 3). This phenomenon is due 

 to respiration as shown by Weysse and Lutz.(8) In these cases 

 we read at the criterion nearest to the appearance of the pulse 

 as felt on the radial artery. 



Infrequently we found subjects who, during the course of the 

 observation, moved their arms and thus caused a marked in- 



