DIAGRAM ILLUSTRATING THE ALIMENTARY CANAL

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Special Systems.—These eight tissues are combined together into various groups of organs or systems for special purposes. These groups are six in number, and include: the circulatory, respiratory, digestive, excretory or secretory, locomotor, and nervous systems. There is also the reproductive system, which has to do with the propagation of the race, and involves many important and vital questions.

We may divide these six into three groups:

There are two in the chest:

(1) The Circulatory system is that by which the blood or liquid food is distributed throughout the body to all the tiny cells. This system includes the heart or force-pump, and the arteries, capillaries, and veins or the three kinds of pipes through which the blood travels.

(2) The Respiratory system is that by which we breathe, and by which the body is fed with oxygen, which gives the blood its bright red color. This system includes the nostrils and mouth, the windpipe and the lungs.

Then there are two in the abdomen, or stomach: