119 



BLOOD PRESSURES IN MAN, NORMAL AND PATHOLOGICAL 311 



etc. ; such would probably yield valuable information as to circulatory 

 conditions. Various observers have noted that in a considerable 

 number of high pressure cases there are no definite symptoms and no 

 evidence of disability; Kulbs (77) found so high a proportion as 20 per 

 cent in this category in a series of 172 males and 116 females with 

 pressures at or above 170 mm. As regards diastolic pressures the 

 American life insurance data are open to criticism from the adoption 

 of the end of the 4th phase as the diastolic index, the latter having been 

 experimentally proved to coincide with the beginning of the 4th phase 

 — in the dog by Warfield (129) and in the sheep by Mac William, Mel- 

 vin and Murray (91). It is certain that serious error may occur in 

 this way especially in young subjects where the duration of the 4th 

 phase may in some cases be long. Thus Melvin and Murray, by care- 

 ful examination in quiet surroundings using a sensitive Oliver auditory 

 tambour, found in 14 young men out of a total of 59 a prolonged 4th 

 phase, ranging between 24 and 55 mm. and averaging 38 mm. The 

 lower limit of the sound was sometimes found to be as low as 10, 14, 20 

 or 22 mm. armlet pressure in healthy subjects with normal systolic 

 pressures and complete absence of any collapsing character in the 

 pulse, etc.; obviously these figures could not possibly represent the 

 actual diastolic pressures. 



Of course such very low readings of the lower limit of the sound are 

 exceptional. Many observers have noted a 4th phase of shorter 

 duration, e.g. Warfield up to 20 mm., Weysse and Lutz (131) not above 

 25 mm., Tixier usually 20 to 30 mm. at ages of 20 to 30 years and in 

 some abnormal subjects 20 to 40 mm., etc. Others have reported 

 figures 5 to 8 mm. (Goodman and Howell, Barach and Marks, Macken- 

 zie, Smith and others). In middle-aged and elderly subjects the ex- 

 perience of the writer is that the sound rarely persists in any important 

 degree (not more than a few millimeters) and consequently the lower 

 limit of sound in these subjects approximately indicates the diastolic 

 pressure- — ^in contrast to the serious discrepancy which may occur in 

 young persons. 



In the insurance statistics referred to the relatively large numbers 

 in the younger groups of subjects (19 to 25 and 25 to 30) would naturally 

 tend to give scope for possible errors in this direction. But such errors 

 would be in the direction of underestimating the actual diastolic pres- 

 sure; on the other hand, the diastolic readings given in the insurance 

 series referred to are by no means low. 



There is sometimes a tendency to undervalue precision of blood- 



PHTSIOLOOICAL REVIEWS, VOL. V, NO. 3 



