7* 



A MANUAL OF VETERINARY PHYSIOLOGY 



volume pulse may show not only every beat of the heart, but 

 even the dicrotic wave (see Fig. 35). 



In connection with pulses the term tension has been employed 

 by pathologists ; thus pulses of high and of low tension have been 



described, and an at- 

 tempt has been made 

 to distinguish between 

 the pathologist's ten- 

 sion and the physiolo- 

 gist's pressure. If ten- 

 sion be defined as the 

 elastic force exerted by 

 the artery on the blood 

 within, it is evident 

 that this bears some 

 distinct relation to the 

 force distending the 

 artery — viz., the blood- 

 pressure ; a high blood- 

 pressure and high ar- 

 terial tension describe 

 the same conditions. In 

 an artery giving a high 

 tension the dicrotic 

 wave is nearly extin- 

 guished, the vessels in 

 fact are so full that the 

 recoil wave makes very 

 little impression on the tense arterial wall ; when blood-pressure 

 is low and the amount of movement in the artery great, the 

 recoil or dicrotic wave is very marked (Figs. 32 and 33). 



The pulse varies in character, depending upon age, condition, 

 and state of the system ; it also differs according to the class of 

 animal. The following table shows the pulse-rate in different 

 animals : 



Elephant - 



Camel - - - - 



Horse - 



Ox 



Sheep - 



Pig 



Dog - 



Certain variations occur in the pulse-rate. It is always much 

 quicker in the young animal than in the adult. The heart of a 

 foal at birth beats 100 to 120 per minute, and that of a calf 90 

 to 130 per minute. As the animal increases in age the pulse- 



Fig. 33. — Curves of Blood-Pressure taken 

 with a Spring Manometer from the Carotid 

 Artery of a Dog (after 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 pressure ; p is the primary 

 elevation. 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. 



