First Book in Physiology and Hygiene by John Harvey Kellogg
page 49 of 172 (28%)
page 49 of 172 (28%)
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~12. How much Work the Heart Does.~--The heart is a small organ, only about as large as your fist, and yet it does an amount of work which is almost beyond belief. Each time it beats, it does as much work as your arm would do in lifting a large apple from the ground to your mouth. It beats when we are asleep as well as when we are awake. When we run we know by the way in which it beats that it is working very fast. Do you know how much a ton is? Well, in twenty-four hours the heart does as much work as a man would do in lifting stones enough to weigh more than one hundred and twenty tons. ~13. The Lymphatics.~--While the blood is passing through the capillaries, some of the white corpuscles escape from the blood-vessels. What do you suppose becomes of these runaway corpuscles? Nature has provided a way by which they can get back to the heart. In the little spaces among the tissues outside of the blood-vessels very minute channels called _lymph channels_ or _lymphatics_ (lym--phat´-ics) begin. The whole body is filled with these small channels, which run together much like the meshes of a net. In the centre of the body the small lymphatics run into large ones, which empty into the veins near the heart. This is the way the stray white blood corpuscles get back into the blood. ~14. The Lymph.~--In the lymph channels the white corpuscles float in a colorless fluid called _lymph_. The lymph is composed of the fluid portion of the blood which has soaked through the walls of the small vessels. The chief purpose of the lymphatics is to carry the lymph from the tissues back to the heart. ~15. Lymphatic Glands.~--Here and there, scattered through the body, are |
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