916. How is the blood propelled through the arteries?
By the very powerful contraction (and alternate dilation) of the thick muscles of the heart, assisted also by the muscular cords of the blood-vessels themselves, and in many instances by the compression of the muscles in which the arteries lie embedded.
917. Why are the capillary arteries capable of receiving the great quantity of blood sent out through the larger vessels?
Because the capillary vessels are so numerous, that though they are infinitely smaller, they are capable of receiving in their minute tubes the whole of the quantity of blood transmitted to them through the larger vessels.
918. Why, when we sit with our legs crossed, do we see the foot that is raised move at regular intervals?
Because the pressure upon the muscles of the leg retards the progress of the blood until it forces itself through the compressed vessels, and thereby imparts a pulsation which moves the leg and foot.
919. Why are capillary blood-vessels found in every part of the system?
Because it is through these small vessels alone that the substances of the body are renewed and changed. Even the larger blood-vessels do not sustain themselves upon the blood which they contain, but receive into their coats numerous capillary vessels by which they are nourished.
"All my bones shall say, Lord, who is like unto thee, which deliverest the poor from him that is too strong for him, yea, the poor and the needy from him that spoileth him?"—Psalm xxxv.