The Bloodvessels. 67 



tracing we judge of the tension of an artery by the height 

 of the up- stroke. In a pulse of high tension the vessel is so 

 full that it can hold but little more ; the upstroke is there- 

 fore a short one, whilst the down-stroke is very oblique. 

 In a pulse of low tension the up-stroke is nearly vertical 

 and high, the down-stroke oblique; the vessel not being 

 very full is capable of holding much more fluid, and its 

 movements are correspondingly affected. 



The Pulse is due to the wave movement set up in the 

 vessels, as the result of the aorta being suddenly distended 

 by the contraction of the left ventricle ; this wave move- 

 ment is very much more rapid than the progress of the blood 

 itself. The pulse-wave is about IS feet in length, and tra- 

 vels at the rate of from 15 to 30 feet a second, whilst the 

 velocity of the blood, even in the large arteries, is not 

 greater than l\ feet per second. Owing to the length of 

 the pulse- wave, the beginning of it is lost in the small 

 arteries and capillaries before the end of it has left the 

 aorta (Foster). 



The pulse will vary in character depending upon age, 

 condition, height of body, and state of the system ; it also 

 differs according to the animal. Colin gives the following 

 table of pulse-rate in different animals : 



The pulse is much quicker in the young animal than in 

 the adult, that of a foal at birth beating 100 to 120 per 

 minute, and of a calf 92 to 132 per minute ;* in old age the 

 pulsations become reduced, and the artery much weaker. 

 As a rule, the higher or bi^er the animal the lower the 



* Colin. 



