Side view of forefoot, showing blood-vessels and nerves: _a_, digital artery; _b_, anterior artery of the os suffraginis; _d_, anterior coronary artery, or circumflex artery of the coronet; _e_′, preplantar ungual artery; _f′_, inferior communicating arteries passing out from the semilunar artery of the os pedis, through minute holes just above the lower border of the bone; they unite to form (_f″_) the circumflex artery of the toe; _A_, digital vein; _B_, superficial venous plexus of coronary band and lateral cartilage; _C_, podophyllous venous plexus; _G_, circumflex vein of the toe; 1, plantar nerve; 2, anterior digital branch of same; 3, posterior digital branch of same; 4, small cutaneous branches of same.] After the arterial or pure blood passes through the capillaries it is collected by the =veins=, to be returned to the heart; then it is driven to the lungs for purification, and is again returned to the heart, from whence it is pumped through the arteries to all parts of the body. [Illustration: FIG. 26. Foot viewed from below and behind: _a_, digital arteries; _c_, arteries of the plantar cushion; _f‴_, small branches of the semilunar artery of the os pedis, which ramify in the velvety tissue of the sole; _A_, digital vein; _B_, venous plexus of the heels or bulbs; _D_, solar venous plexus; _G_, circumflex vein of the toe; 3, posterior digital branch of the plantar nerve; 4, cutaneous branches of the same.] The veins are more numerous than the arteries; they have thinner walls, and the larger ones are provided with =valves= that prevent the impure blood from flowing backward. The veins carry impure or =dark-red= blood towards the heart, and if one is opened the dark blood flows in a steady stream; it does not spurt. The great number of veinlets in the lower parts of the foot form a complex net-work (plexus) of vessels which are in such manifold and close union with one another that checking the flow of blood in one part does not seriously interfere with the flowing of the blood towards the larger veins. The following are the most important of these net-works of veins or venous plexuses: (1) the _solar venous plexus_ (Fig. 26, _D_); (2) the _podophyllous venous plexus_ (Fig. 25, _C_); (3) _superficial coronary venous plexus_ (Fig. 25, _B_); (4) _bulbar venous plexus_ (Fig. 26, _B_). All these plexuses of small veins contribute to form the _digital veins_ (Figs. 25 and 26, _A_).