112 



304 J. A. MACWILLIAM 



with two independent pressure bags applied to the upper arm instead 

 of the wrist; this is the best form of oscillatory apparatus at present 

 available. 



Experience has emphasised the importance of combining the tactile 

 systolic index with the auscultatory systolic as a routine 'procedure, 

 recommended by MacWilliam and Melvin (90) in 1914; the latter index 

 should always show a higher value when the estimation is correctly 

 made. This of course necessitates the use of one of the various forms 

 of apparatus that provide for the retention of the auditory receiver 

 in position, leaving the hands free, e.g., the Baumanometer, the Tycos, 

 the Laubrey sphygmophone, the Oliver tambour, etc. The checking 

 of the auscultatory systolic by the tactile systolic is essential for more 

 than one purpose — as a guarantee of the proper functioning of the 

 auditory apparatus, and in guarding against error which may some- 

 times arise after prolonged or repeated armlet compression. Repeti- 

 tion may be needed to correct the disturbances in pressure due to 

 excitement, etc., at the first compression; as is well known, subsequent 

 readings are frequently decidedly lower — until a constant level is 

 reached, the residual pressure. Some persons under pathological con- 

 ditions are specially liable to show a decided rise of pressure from re- 

 peated or continued compression especially when the arm becomes 

 congested distally to the compressing armlet. Effects (reflex, etc.) 

 from repeated compression by the armlet come into question, described 

 by Gallavardin with Haour (53) and Tixier (54) as involving differ- 

 ent types of pressure changes, rises, falls, etc. 



The present writer has found important disturbances of the auditory 

 indications in a certain number of subjects, as a result of compression 

 which involves marked turgescence of the hand and forearm — a cutting 

 down of the systolic index with a rise of the diastolic. Sometimes 

 at a later stage of prolonged compression there is enfeeblement or dis- 

 appearance (at variable points) of all the sounds below the upper 

 region of sound, in the neighbourhood of the systolic level. Such 

 disturbances may occur while the actual blood pressure is not changed 

 — as shown by the tactile systolic index remaining unaltered; thus 

 incorrect measurements including an unduly restricted pulse pressure 

 may be obtained in these cases by the use of the auscultatory method 

 alone — unchecked by the tactile method. Some subjects are excep- 

 tionally susceptible to the development of such disturbances; the 

 significance of these differences in behaviour has not been determined. 



Another purpose for which repeated compression has been used is to 



