100 



PHYSIOLOGY AND HEALTHS 



CHAPTER II. 



Veins. Distribution. Capillaries. System of general Circula- 

 tion. Situation of Arteries and Veins. Pulmonary Arteries and 

 Veins. Double Circulation. 



FIG. XII. Greed Veins. 



a, Heart. 



b, Ascending vena cava. 



c, c, Subclavian veins. 



d, d, Brachial veins, in the arms. 



e, e, Veins from the outside of the 

 head. 



f> /> Veins from the brain. 



g, Descending, or abdominal vena 

 cava. 



h, h, Veins from the kidneys. 



i, i t Great branches of veins in the 

 groins. 



k, k. Veins from the lower extrem- 

 ities. 



' 215. The veins also connect the 

 heart with every part of the body. 

 Their coats are thinner and softer 

 than the arteries. They collapse 

 when they are empty. They are 

 easily compressed, as can be 

 shown by pressing the veins on 

 the back of the hand. They 

 have valves, which open and allow 

 i,he blood to pass toward the 

 heart, but close and prevent it 

 flowing backward. 



216. One large vein, the vena 

 cava, opens into, the heart,, and 

 carries all the blood of the body 

 into it. The upper part of this vein, the vena cava ascen- 

 dens, extends upward, and sends branches to the head and the 

 arras. The lower part, the vena cava descendens, passes 



