360 APPENDIX. 



besides the absence of jets, may at once be known from 

 arterial blood by its dark color. 



Capillary Vessels. The arteries having conveyed the 

 blood to all parts of the system, it is taken Up by the 

 capillary vessels, which form the connection between the 

 arteries and veins, and is thus transmitted to the latter. 

 These vessels are called capillary, from capillus a hair, 

 on account of their extreme minuteness. They pervade 

 all parts of the system, and when the finger is punctured 

 by a needle, more or less of them are wounded, and dis- 

 charge their contents. 



Distribution of the Veins. The veins are distributed 

 in the same manner with the arteries, but they are far 

 more numerous, and as a whole, are considered more^ 

 capacious than the arteries. - The veins are furnished 

 with valves, composed of folds of the inner membrane, or 

 coat of the vein. They open toward the direction of the 

 current of the blood, and their use appears to be to pre- 

 vent the fluid from returning from the heart towards the 

 surface of the body. In the lower limbs these valves are 

 very important, as they support the column of blood, 

 which to all appearance, would otherwise rupture the 

 veins. 



Particular Veins. With respect to the names and 

 courses of the several veins, supplying the different parts 

 of the system, it is hardly necessary to speak in a book 

 so very elementary as this. We have already, p. 105, 

 figured and described the office of the large veins near 

 the heart, called the ascending and descending, vena cava. 

 Many of the veins, like the arteries, are named from the 

 parts through which they pass, as the axillary veins, the 

 subclavian veins, the radial vein, &c 



Hartford, Sept., 1847. 



