510 



Messrs. M. Flack, L. Hill, and J. McQueen. 



From a case of aortic disease having an aberrant radial artery we have 

 taken tracings, using the Dudgeon sphygmograph with weight extension. 

 The absence of the plethysmograph effect and of disturbance from venae 

 comites — there are none accompanying the aberrant artery — was thus 

 secured. In the tracing (fig. 1) the external pressure in the armlet at the 

 upper arm was, to begin with, mm., then raised to 30 mm. The size of 

 the initial pulse beat was regulated by the weight in the pan of the extension 

 apparatus ; some little skill is needed to secure the proper weight to show 

 the phenomenon in a marked fashion. 



Fig. 1. 



The tracing demonstrates that there is an increase in the systolic pressure 

 in the radial artery as a result of compressing the upper arm ; there is 

 consequently an increase in the pulse-pressure range. 



Corroboration of these tracings has been obtained by placing one armlet 

 on the calf and another on the thigh of a boy. In normal boys we find the 

 thigh reading to be higher than that of the calf.* 



Boy. 



Systolic pressure (horizontal posture). 



Thigh. 



Calf. 



I. 



II. 

 III. 



mm. of Hg. 

 165 



155 

 105 



mm. of Hg. 

 135 



140 when 60 mm. Hg was maintained in the thigh armlet. 



130 „ 

 120 



135 „ 40—50 mm. Hg „ „ 

 80 



90 „ 



* In the case of two patients we have observed a systolic pressure considerably higher 

 in the calf than in the thigh ; e.g., 175 thigh, 300 calf, upper part, and 225 mm. Hg lower 

 part of leg. These differences of pressure obtained in both legs. It has been suggested to 

 us that the higher reading in the leg may be due to protection of the artery from compression 

 by fascinse. It is difficult to see how this can come about, and we are at present unable to 

 offer an explanation other than one based on the observations detailed in the following 

 paper. The difference was certainly not due to resistance to compression on the part of 

 the arterial wall, for the dor^alis pedis artery in these patients offered no unusual 



