The Velocity of the Pulse Wave in Man. 301 

 Table I. 



I. Fig. 6, Koy's Paper. — Inferior Vena Cava of Cat. 



p (mm. of Hg) 



5 



10 



20 



30 



40 



v (m.p.s.) 



1 -55 



2*2 



3 ;l 



4-3 



5-0 



II. Fig. 7.— Femoral Artery of Eabbit. 







20 



40 



60 



80 



100 



120 



140 



160 



V 





2-21 



2 27 



2-12 



2 33 



3 10 



5-05 



7-15 



9-22 





III. Fig. 9.- 



-Carotid of Eabbit, immediate!} 7 after death. 





p ...... 



20 



40 



60 



70 



i 80 



100 



120 



140 



160 



V 



3 15 



3-15 



3 08 



3-1 



J 3-48 



4-7 



7 



1 



10-7 



17 -8 



IV. Fig. 11.— Thoracic Aorta of Cat. 



P 





20 



40 ' 



60 



80 



100 



120 



140 



160 







3 4 



3-6 



3 5 



3-6 



3-6 



3-8 



4-3 



5-4 



V. Fig. 10. — Carotid of Emaciated Dog, suffering from ill-treatment and 



chronic illness. 



p 



20 



40 



60 



80 



100 



120 



140 



i. V 



3 1 



4 



5-1 



6-0 



7-3 



8 -4 



8-9 



The most striking fact about, these figures is that in a normal healthy 

 artery (II, III, and IV) the velocity is constant as the pressure rises from a 

 low value up to about 80 mm., after which it increases, at first slowly and 

 then more rapidly. At high pressures the velocity is very considerably 

 increased. In V the velocity increases considerably throughout. Secondly, 

 the velocities in II, III, and IV, at pressures of 80 mm. (about equal to the 

 normal diastolic pressure in man), are noticeably less than those observed in 

 man. This may be characteristic of the animals investigated, but it seems 

 more probable that it is due to the following factor. All living tissues, and 

 especially arteries and muscles, show the phenomenon of elastic " after- 

 action," continuing to extend for some time if the load or tension be main- 

 tained. Roy attempted to avoid errors due to this by making his observations 



