First lesson in zoology : adapted for use in schools . chamber, opening behindinto the pharynx, from which one tubeleads to the lungs, I, and another to thestomach, /; A, the heart; /c, a kidney;s, the sympathetic nervous the stomach, /, the intestinaltube leads through the abdominal cav-ity to the posterior opening of the ali-mentary canal. intestine. Thus there are two tjavities,—^the nervous oneabore, and the visceral one below, the backbone (Figs. 143, 138 FIBST LESSONS IN ZOOLOGY. 144). In this respect the backboned animals differ fromthe backboneless or invertebrate animals, i
First lesson in zoology : adapted for use in schools . chamber, opening behindinto the pharynx, from which one tubeleads to the lungs, I, and another to thestomach, /; A, the heart; /c, a kidney;s, the sympathetic nervous the stomach, /, the intestinaltube leads through the abdominal cav-ity to the posterior opening of the ali-mentary canal. intestine. Thus there are two tjavities,—^the nervous oneabore, and the visceral one below, the backbone (Figs. 143, 138 FIBST LESSONS IN ZOOLOGY. 144). In this respect the backboned animals differ fromthe backboneless or invertebrate animals, in which there isbut one body-cavity, with the nervous system usually situ-ated on the floor of this cavity. Vertebrates have a true heart, with one, generally two,auricles, and one or two ventricles, and, besides arteries andveins, a system of capillary vessels, which are minute tubesconnecting the ends of the smaller arteries with the smallerveins. There are no genuine capillaries in the lower ani-mals exactly comparable with those of Fig. 145.—A diagrammatic section across the body in the chest region, x. theneural canal, which contains the spinal cord; the black mass surrounding itis a vertebra; a, the gullet, a part of the alimentaiy canal: ft, the heart; sy,sympathetic nervous system; 11, lungs; the dotted lines around them are thepleurae; rr, ribs; st, the breastbone. The blood is red in all the vertebrates except the lance-let, and besides red, contains white corpuscles. Whilefishes and tadpoles breathe by gills, all land and amphibiousvertebrates breathe the air directly by lungs connected by awindpipe {trachea) with the mouth. The nervous systemconsists of a brain and spinal cord. The brain consists offour pairs of lobes, , the olfactory lobes, cerebral hemi-spheres, the optic thalami with the pineal gland, and theoptic lobes; besides these lobes, which are arranged in pairs,there are two single parts of the brain, the cerebellum andthe beginning
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1894
