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: ... 278 Chapter XII. THE SKELETON OF THE BABBIT. Lepui cuniculus. In the early stages of development the skeleton of the rabbit consists entirely of cartilage. This primary cartilaginous skeleton agrees in general plan with the skeleton of the dogfish, and may be taken as representing corresponding stage in the evolution of mammals. The skeleton of the adult rabbit is made up of bone, together with a small amount of cartilage. The bones are of two chief kinds. (1.) Cartilage-bones are so called from their arising in direct relation with the pre-existing cartilage. They make up the greater part of the adult skeleton. (2.) Membrane-bones are developed independently of the primary cartilaginous skeleton, and are almost confined to the head. They are to be regarded as dermal bones which have lost their connection with the skin, and become in many cases firmly united with the underlying cartilage and cartilage-bones: they are morphologically equivalent to the bony plates forming the bases of the scales in the dog-fish. The sesamoid bones form a third class. These are small nodules of bone developed within the tendons of certain of the limb-muscles, close to the joints: they modify the action of these muscles by altering the direction in which they pull. The teeth of the rabbit are cutaneous structures, comparable to the scales or teeth of the dog-fish; they are, however, in the adult so intimately associated with the hones of the jaws that they may conveniently be described with the skeleton. The hairs and claws, which are special developments of the epidermis, or surface-layer of the skin, will be described in the next chapter. The rabbit's skeleton may be divided, like that of the dogfish, into axial and appendicular portions, which will be dealt with successivel...