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SPECIAL PHYSIOLOGY 



system which may be determined with the help of the sphygmograph. 

 Make a list of the precautions to be observed in the use of the sphyg- 

 mograph. 



The Carotid Pulse. 



One will frequently experience difficulty in taking the radial pulse; 

 in fact, not more than one person in three or four is a favorable 

 subject for this observation. The reason for this is not far to seek. 

 Anything beyond a moderate development of the musculature of 

 the forearm is accompanied by such development of the tendons 

 and of the styloid process of the radius that the artery is quite in- 

 accessible for the sphygmograph-foot as usually constructed. A 

 moderate deposit of subcutaneous fat also obscures the radial 

 pulse and makes the use of the sphygmograph most unsatisfactory. 



Fro. 51 



Porter's carotid sphygmograph : R, receiving tambour in form of open bell, that is pressed 

 against the throat over the common carotid ; T, tracing tambour with small, thin membrane and 

 light lever. 



The simple sphygmograph devised by Dr. Porter, of Harvard, 

 enables one to overcome some of the difficulties mentioned above. 

 This instrument consists (1) of a very small and delicately adjusted 

 recording tambour with high magnification and a delicate tracing 

 point; (2) of a receiving tambour not over 2 cm. or 3 cm. in diameter 

 and at least 1 cm. deep, connected with the recording tambour 

 through a 50-cm. piece of pressure tubing, which is provided with a 

 side vent closed by a clamp. For the receiving tambour a small 

 thistle tube may be used. (See Fig. 51.) 



