THE PULSE. 



ing pulse, and its unnatural excess of the hard and tense 

 one. 



The elastic and muscular contraction of an artery may 

 also be regarded as fulfilling a natural purpose when, the 

 artery being cut, it first limits and then, in conjunction 

 with the coagulated fibrin, arrests the escape of blood. It 

 is only in consequence of such contraction and coagulation 

 that we are free from danger through even very slight 

 wounds ; for it is only when the artery is closed that the 

 processes for the more permanent and secure prevention of 

 bleeding are established. 



Mr. Savory has shown that the natural state of all arte- 

 ries, in regard at least to their length, is one of tension 

 that they are always more or less stretched, and ever ready 

 to recoil by virtue of their elasticity, whenever the oppos- 

 ing force is removed. The extent to which the divided 

 extremities of arteries retract is a measure of this tension, 

 not of their elasticity. 



From what has been said in the preceding pages, it 

 appears that the office of the arteries in the circulation is, 

 1st, the conveyance and distribution of blood to the several 

 parts of the body ; 2nd, the equalization of the current, and 

 the conversion of the pulsatile jetting movement given to- 

 the blood by the ventricles, into an uniform flow ; ^rd, the 

 regulation of the supply of blood to each part, in accord- 

 ance with its demands. 



The Pulse. 



The jetting movement of the blood, which, as just stated, 

 it is one of the offices of the arteries to change into an uni- 

 form motion, is the cause of the pulse, and therefore needs 

 a separate consideration. We have already said, that as the 

 blood is not able to pass through the arteries so quickly as 

 it is forced into them by the ventricle, on account of the 

 resistance it experiences in the capillaries, a part of the 



