A close relation exists between the soil, plant, and the animal. One really cannot exist without the other to fulfill its destiny. A soil without plant or animal growth is barren, devoid of life. The soil comes first; the elements contained in it and the air are the basis of plant and animal life. The body of the animal is made up of the identical elements found in the plant, yet the growth of the plant is necessary to furnish food for animal life. The plant takes from the soil and from the air the simple chemical elements, and with these builds up the plant tissue which, in its turn, is the food of the animal. The animal cannot feed directly from the soil and air; it requires the plant first to take the elements and to build them into tissue. From this tissue animals get their food for maintenance and growth. Then the animal dies; with its decay and decomposition comes change of animal tissue, back to soil and air again; back to single simple elements, that new plants may be grown, that new plant tissue may be made for another generation of animal life. Thus the plant grows out of the soil and air, and the decay of the animal plant life furnishes food for the plant that the plant may furnish food for the animal. Thus we see the cycle of life; from the soil and air come the soil constituents. [Illustration: CIRCULATION AND DIGESTION 1 Mouth, 2 Pharynx, 3 Trachea, 4 Jugular Vein, 5 Carotid Artery, 6 Œsophagus, 7 Posterior Aorta, 8 Lungs, 9 External Thoracic Artery, 10 Left Auricle, 11 Right Auricle, 12 Diaphragm, 13 Spleen, 14 Stomach, 15 Duodenum, 16 Liver, upper extremity, 17 Large Colon, 18 Left Kidney and its Ureter, 19 Floating Colon, 20 Rectum, 21 Anus, 22 Bladder, 23 Urethra, 24 Small Intestine, 25 Cæcum, 26 Venous Supply to the Foot, 27 Posterior Tibial Artery, 28 Internal Metatarsal Vein, 29 Internal Metatcarpal Vein, 30 Posterior Radial Artery, 31 Metacarpal Artery, 32 Vertebral Artery, 33 Superior Cervical Artery, 34 Anterior Dorsal Artery.] =Meaning of Plant Building.=--Before the single simple elements were taken into the plant, they were of little value. The animal could not use them for food, they could not be burned to furnish heat, and they stored up no energy to carry on any of the world’s work. What a change the plant makes of them! So used, they become the source of the animal food, and, as food, they contain five principal groups with which the animal is nourished. These five groups are the air, water, the protein compounds, the nitrogen free compounds, such as starch, crude fiber, sugar and gums, and the fat or ether extract, as it is called. DIGESTION OF THE FOOD