GENERAL ANATOMY OF THE VEINS. 229 



to those who are in the habit of injecting them for anatomical 

 study. By partially filling the vessels with a thin fluid and 

 then throwing in more fluid per saltum, we may readily produce 

 a sort of artificial pulse. 



Of the Veins. 



These tubes, which return to the heart the blood carried 

 from it by the arteries, are more numerous than the arteries, and 

 often are larger in diameter. 



They generally accompany the arteries, and very often two 

 veins are found with one artery. These are called the vena 

 comites. 



Accompanying the larger arteries of the body, we usually 

 find but one attendant vein of proportionate size. It is the 

 smaller arteries, and especially those of the extremities, that 

 have generally running by their sides, and mostly in very close 

 connection, two venous trunks (vena comites) all of which are 

 invested in one common sheath. 



In addition to these last mentioned veins, which may also be 

 called deep-seated, there are many subcutaneous veins which 

 appear on almost every part of the surface of the body. 

 There is a third division of the venous system known under 

 the name of sinuses, found in the cranium, the diploe and cells 

 of the bones, and in the substance of the uterus. These are 

 all lined in their interior by the common lining membrane of 

 the veins. But they differ from the other veins in regard to 

 their outer tunic, which is formed of the dura mater in the 

 cranium, of the cellular lining membrane found in the cells of 

 the bones ; and in the uterus apparently of the substance of 

 that organ. 



The capacity of all the veins is much greater than that of 

 all the arteries. 



Those subcutaneous veins which are of considerable size, 



communicate very freely with each other, and also with the 



deep-seated veins. They are found just below the skin in the 



layers of the superficial fascia, which latter membrane they 



VOL. ii. 20 



