I 111. «)\\ |\ 1 HI. AICi 



precede this notch can not be related to d 



tin- heart Evidently, then, th< iry pu 



equal significance, by far the must important being that which 



immediately after tin- Becond sound, called tl 



•h in front of it being called the dicrotic no \ econd 



waves urring before the dicrotic . 1 1 1 •-« I j 



ur <>ii the ascending limb of the main pulse ' • sometii 



do, they are « • ; i II • * » L anacr Vi the di< 



called postdu 



The relative importance of the dicrotic, in comparison with tl.. 

 dicrotic ami postdicrotic waves, is furtl • 

 it alone is Been on a Bo-called hemataugram, which 



tained by allowing a fine stream of M 1. escaping from a pinhoh 



in the -\\ a 1 1 of an artery, to impinge upon a movii _ of white blot- 

 ting paper. That such a tracing Bhowa a dicrotic but no s ndary wa 



indicates thai only the former is presenl in the bl 



that the "tip londary waves must be produced bj some 



arising either in the elastic tissue of the walls of the blood 



in the elastic propertii the instruments used for taking the p 



tracing. 



The Dicrotic Wave. Because of its obviously gri rnifican 



shall first of all consider the exact cause of tin- dicrotic wave and 



h preceding it. Theoretically, two possible - niigl * lain 



the wave: either it is due to some secondary wave set up at I 

 or it is dependent upon wa- lected from the periphery of t ; 



culation hack along the blood Btream, just sondary wavi 



fleeted from the walk of a tub of water when a stone is thrown in the 



center. In considering this s ml possibility, we art 



the assumption thai at the ends of th<- arterial ra then 



stance to the onward movemenl of blood, Tl [uent brand 



which ' urs when the arteriole '.pillar 



i many opportunitii ction of pull 



rt, hut these waves must be reflected at such varying 

 the art. -rial system thai there can be little opportunity 

 come added together so ;is m a wavi 



make itself p tible in the blood flowing in the 



wa\ relatively bo small and they occur ich different timi 



the lift result «>t" their addition, s«> • 

 wavi oncerned, must 1>.- practically nil. Notv 

 Biderations, it is possible thai under - i uses 



of high arterial tension, certain of th»> pred 



ma\ be 'hif d> tin- a! 



