A Junior Course of Pracical Zoology - Softcover

Reseña del editor

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1892. Excerpt: ... Chapter XIII. DISSECTION OF THE EABBIT. The rabbit may be taken as a type of the Mammalia; and the following points should be noted as characteristic of the great majority of the members of the group. The distinguishing features of the skeleton have been noted in the preceding chapter. Externally, the body is covered with hair: the urinogenital and anal apertures are distinct from each other: and there are large external ears. As regards the viscera:--Mammary glands are present, opening to the exterior on teats placed on the ventral surface of the body. The heart has four chambers: there is a single aortic arch in the adult, formed from the fourth left arch of the embryo: the blood is hot, and the red corpuscles nonnucleated. There is a complete diaphragm; and the lunn-s, which are not attached to the ribs, are completely surrounded by pleurae. The ureters open directly into the bladder. In the brain there is a corpus callosum, connecting the hemispheres; and corpora quadrigemina in place of corpora bigemina, or four optic lobes in place of two. The cochlea is coiled spirally. The ova are extremely small, and are retained within theuterus during almost the whole period of their development. The embryo receives a constant supply of nutriment direct from the mother by means of the placenta, a structure in which the blood-vessels of the embryo and of the mother are brought into very close relation, so that diffusion can readily take place from one to the other. In the following account the several systems are described one by one, in order that each may be studied in its entirety as far as practicable, and the mutual relations of its several parts demonstrated. This method is the best, and should be followed whenever possible. If, however, it is intended to ...