5 i6 MANUAL OF ZOOLOGY SECT. 



of the foetus and that of the parent, and nourishment 

 is thus received by the former from the latter. 



After birth the young Rabbits are nourished for a time 

 wholly by the milk, or secretion of the mammary glands of 

 the mother. 



The following are the principal general features which 

 characterise the Mammalia as a class : 



The Mammalia are air-breathing vertebrates, with warm 

 blood, and with an epidermal covering in the form of hairs. 

 The bodies of the vertebrae in nearly all Mammals are 

 ossified each from three independent centres, one of which 

 developes into the centrum proper, while the others give 

 rise to thin discs of bone the epiphyses. Also characteristic 

 of the spinal column of Mammals are the discs of 

 fibre-cartilage termed inter-vertebral discs, which intervene 

 between successive centra. 



The skull has two condyles in connection with the atlas, 

 instead of the single condyle of the Reptiles and Birds ; and 

 the lower jaw articulates with the skull in the squamosal 

 region without the intermediation of the separate quadrate 

 element always present in that position in Birds and 

 Reptiles. Each of the long bones of the limbs is composed 

 in the young condition of a central part or shaft and 

 terminal epiphyses, the latter only becoming completely 

 united with the shaft at an advanced stage. In the pectoral 

 arch the coracoid of the Birds and Reptiles is usually 

 represented only by vestiges, which unite with the scapula 

 in the adult. 



Mammals are typically diphyodont, i.e., have two sets of 

 teeth a milk or deciduous set, and a permanent set : some 

 are monophyodont, i.e., have only one set. The teeth are 

 thecodont, i.e., the base of each tooth is embedded in a 



