Fig. 25.
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.
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]).
Nerves are roundish white cords which come from the brain and spinal cord; they generally accompany arteries. They divide and subdivide into smaller and smaller branches till they become invisible to the naked eye and are lost in the tissues. The nerves that are found in the foot come from the spinal cord, and because the largest nerves of the foot accompany the digital arteries they are called digital nerves ([Fig. 25, 1]). The branches ramify throughout all parts of the foot except the horny box and the hair. Nerves, according to their use or function, are classed as motor and sensory. The motor nerves end in muscles which they stimulate to action and control. The sensory nerves terminate in the skin and in the soft tissues just under the horny box or hoof (pododerm), and render these parts sensitive; that is, they convey certain feelings, as, for example, the pain caused by bruising, pricking, or close-nailing, to the brain and consciousness.