too 



A MANUAL OF PHYSIOLOGY 



physics, to the measurement of blood-pressure. Ludwig 

 and others improved this method by making the manometer 

 self-registering by means of a float in the open limb, sup- 

 porting a style which writes on a revolving drum, the whole 

 arrangement being called a kymograph. (For the method 

 of taking a blood-pressure tracing, see p. 185.) 



For reasons already mentioned the mercurial manometer 

 is better suited for measuring the mean blood-pressure, or 

 for recording changes in the pressure which last for some 

 time, than for following the rapid variations of the pulse- 

 wave. For the latter 

 purpose, one of the 

 class of elastic mano- 

 meters is required 

 (p. 82). 



A blood - pressure 

 tracing taken from an 

 artery with a mano- 

 meter of this sort 

 yields the truest pic- 

 ture of the pulse-Wave 

 which it is possible 

 to obtain, because the 

 reproduction of it is 

 the most direct. The 

 fact that such a trac- 

 ing shows a close 

 agreement with the 

 trace of a good sphyg- 

 mograph applied to the corresponding artery on the other 

 side, is a striking proof of the general accuracy of the sphyg- 

 mographic method for physiological purposes, and enables 

 us to guide ourselves in transferring to man, in whom, of 

 course, the sphygmograph can alone be used, the information 

 derived from direct manometric observations in animals. 



For the same reason it is unnecessary to discuss the 

 manometric tracings, as regards the pulsatory phenomena, 

 in all their details. It will be sufficient to say that while 

 the form of the blood-pressure pulse-curve varies with the 



FIG. 29. CURVES OF BLOOD-PRESSURE TAKEN 

 WITH A SPRING MANOMETER FROM THE 

 CAROTID ARTERY OF A DOG (HURTHLE). 



When i was taken the blood-pressure was high ; 

 2 corresponds to a medium, 3 to a low, and 4 to 

 a very low blood- pressure ; p is the primary eleva- 

 tion this and the succeeding elevations between 

 p and a are called systolic waves ; the systolic 

 waves are followed by a marked elevation d, which 

 corresponds to the dicrotic wave. 



