Healthy living . ies Fig. 51.—The blood vessels ofthe hand. page 102, we can see the ships that sail in the blood cannot very well see the blood actually flowing through our own blood ves-sels even with a microscope; but it is possible to see the blood flowing in the vessels of certain animals which have a very thin, transparent skin. The foot of a frog, for example, has a very delicate skin between the toes; and if the frogs foot is held under a microscope, one can see a wonderful sight. The thin part of the foot between the toes is full of small blood vessels; and each of these, un
Healthy living . ies Fig. 51.—The blood vessels ofthe hand. page 102, we can see the ships that sail in the blood cannot very well see the blood actually flowing through our own blood ves-sels even with a microscope; but it is possible to see the blood flowing in the vessels of certain animals which have a very thin, transparent skin. The foot of a frog, for example, has a very delicate skin between the toes; and if the frogs foot is held under a microscope, one can see a wonderful sight. The thin part of the foot between the toes is full of small blood vessels; and each of these, under the microscope, is seen to be crowded wdth littleround discs, like those whichare dra^vn in Fig. 52. Theyare not still and quiet, how-ever, as you see them in thepicture, but are rushing pastat a great speed and tum-bling about in the stream, as Fig. oxygen-carry- ^hey are carried along by theing cells of the blood, as blood flow. These tiny shipsthey appear under the are the red cells of the microscope in the tiny It is the red cells which carry blood vessels of the foot of a frog. oxygen from the lungs to the 124 HEALTHY LIVING other organs, and in the tissues exchange the oxygen forcarbon dioxide. They carry the carbon dioxide to thelungs, where they give it up and take on a new cargoof oxygen in its place. These red cells are so abundant in the blood thatthey give it the red color. The liquid in which theyfloat is not red at all, but a yellowish straw-color. There is another kind of cell in the blood streamwhich might be likened to a warship, since we havecompared the red cells to merchant ships. These arelarger and less numerous than the red cells. As theyare whitish in color, they are called the white attack and destroy harmful things, like diseasegerms, which enter the blood. When we ^^get overan attack of influenza or typhoid fever or a cold in thehead or some other disease, it is largely because of theactivity of these white cells in de
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