Animal life in the sea and on the land . with teeth. The foodis mostly cut and divided in the mouth and mixed with saliva, after which it is swal-lowed and digested, and thenutritious portions are ab-sorbed into the blood. 13. The Heart.—The heartof all vertebrates containsat least two chambers, and inthe higher classes of animalsit has four distinct chambers are suppliedwith valves at their openingswhich allow the blood to passthrough, but which close insuch a manner as to preventits return in the opposite di-rection. 14. Circulation of the Blood.—Dr. Harvey, in 1619, was the f
Animal life in the sea and on the land . with teeth. The foodis mostly cut and divided in the mouth and mixed with saliva, after which it is swal-lowed and digested, and thenutritious portions are ab-sorbed into the blood. 13. The Heart.—The heartof all vertebrates containsat least two chambers, and inthe higher classes of animalsit has four distinct chambers are suppliedwith valves at their openingswhich allow the blood to passthrough, but which close insuch a manner as to preventits return in the opposite di-rection. 14. Circulation of the Blood.—Dr. Harvey, in 1619, was the first person that taught the great fact of the circula-tion of the blood, and it is now so well understood as toattract but little attention. We know that the blood ofliving animals is continually flowing to every part of thebody through closed tubes, or blood-vessels, as they arecalled, the arteries being employed in carrying it fromthe heart, and the veins in returning it again. 15. The Blood. — We are accustomed to think of the. Fig. 121.—Fore and Hind Leg ofa Tapir. S, scapula; I, ilinm, or shinbone ofpelvis; H, humerus; F, femur; O,olecranon, or tip f the elbow ; P, pa-tella; U, ulna; T, tibia; R, radius;Fi, fibula. BACKBONED ANIMALS. 191 blood simply as a red fluid, whereas, upon examination,it is found to be a clear liquid, almost without color, inwhich floats a multi-tude of minute par-ticles or corpuscles,so exceedingly smallthat they can be dis-covered only with apowerful of these corpus-cles are red, othersare white. The redcorpuscles have a ten-dency to run togeth-er into piles like but-tons on a string, andthey are so numer-ous as to tinge the blood with their red color (Fig. 122).16. The Breathing of Vertebrates.—We shall find a greatdifference among these animals with regard to their man-ner of receiving a supply of fresh air. Fishes and am-phibious animals are furnished with gills, and derive theirsupply of air from the water, but the hi
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1887
