OF THE ARTERIES GENERALLY, 121 



fully supplied with arteries according to their nature : 

 secreting organs have usually large trunks, as the kidneys, 

 spleen, &c. Arteries are likewise themselves furnished with 

 arterial and venal branches ; for the nourishment of their 

 tubes. They are chiefly supplied with nervous energy by 

 the sympathetic system of nerves ; which accounts for their 

 being little endowed with feeling. It also renders easy of 

 explanation their being possessed of eccentric powers ; such 

 as directing more blood to the face, as in blushing ; and 

 driving more blood to a part, as in local inflammation ; while 

 their action in neither case can be controlled by the will. 



The evident use of the arteries is to convey the blood 

 from the heart to the different parts of the body ; thus 

 keeping up the vital principle in these parts, by being the 

 bearers of nutriment and heat. An intimate knowledge of 

 their functions, and a w^ell -grounded acquaintance with their 

 situation, is therefore essentially necessary to the veterinary 

 surgeon. 



As the use of the arteries is to convey the blood from 

 the lieart ; so the heart itself appears to be the first, but not 

 the only agent exerted in its propulsion through the vessels. 

 And as the force of the heart decreases with distance ; so 

 there is, at last, a column pressed on in almost a continuous 

 stream, by the force from behind : thus when a very small 

 artery is divided, there is a regular flow, with scarcely any 

 jet : this, however, only takes place in their minutest 

 branches. We thus see why there is no pulsation in the 

 veins ; they receive the blood from the arteries in one equa- 

 ble stream. Pulsation is a certain sensation caused by the 

 artery ; which, from various experiments, is found to arise 

 from its being alternately in a state of distention and relaxa- 

 tion. It appears that, when the ventricles contract, and 

 force the blood into the arteries, the pressure of the fluid 

 occasions a distention of their coats : when the ventricles 

 cease to act, and become contracted, the impetus against 

 the sides of the vessels ceases ; and now the coats of the 

 arteiy contract also, and lessen its size. 



Absorbents are distributed to every part of the body ; it 

 is true we cannot see them, neither are they to be traced, 

 save by the very finest of liquid injections ; but their 



