CHAPTER XXIV 



MAMMALIA 



The rabbit is a member of a class of backboned animals 

 which includes man himself, and is on that 

 account usually regarded as the " highest " group 

 in the animal kingdom, though it would be hard 

 to show that they are more highly organised 



than, for instance, the birds. They are known as Mammals 



Mammalia : 

 Prototheria, 

 Metatheria, 

 and Eutheria. 



Fig. 334. — The Duckmole (Ornithorhynchus). — From Thomson. 



or Mammalia from their possessing milk glands, by which 

 the young are nourished for some time after birth. They 

 are warm-blooded, their skin bears hairs, the heart consists 

 of two auricles and two ventricles and gives rise to a single 

 aortic arch, which curves to the left side, there are two 

 occipital condyles, and the lower jaw articulates with the 

 squamosal bone. One little group of mammals, found in 

 Australia, Tasmania, and New Guinea and known as 

 Prototheria or Monotremata, differs widely from the rest in 



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