CHAPTER XI 

 LEPUS CUNICULUS 



A Mammal Lepus cuniculus, the Rabbit Introduction External characters 

 Skin Muscular System Skeleton and the Skull of the Dog. 



A Mammal Lepus cuniculus, the Rabbit. 



The Class Mammalia includes the highest animals alive in the 

 world and reaches its culmination in man himself who, while not so 

 highly specialised structurally as some other forms, is nevertheless 

 characterised by such a high degree of mental development that he 

 must be regarded as the dominant form in the class. Mammals 

 are ccelomate, chordate, craniate animals and so possess all the 

 general characters implied by those terms. In certain points they 

 resemble the frog much more closely than the dogfish. Thus, for 

 example, they possess an endoskeleton composed mainly of bone 

 and modified pentadactyl limbs. The pericardium lies within the 

 coelom, respiration in the adult takes place by means of lungs and 

 not gills and the air passage opens within the buccal cavity by a 

 pair of internal nares. Lastly the urinary bladder is not an enlarge- 

 ment of the kidney duct, but an outgrowth of the cloaca of the 

 embryo. 



The differences from both the dogfish and the frog are numerous 

 and important, and practically constitute the diagnostic characters 

 of the class. It is only necessary to call attention to the main ones 

 here, since the detailed differences will appear in the course of an 

 examination of a particular example. A well-marked exoskeleton 

 is present in the form of hairs, each springing from an encasing 

 sheath or follicle, constituting in most species a more or less complete 

 covering for the body and also as claws, nails or hoofs occurring at 

 the ends of the digits. The skin also bears two kinds of glands, 

 distinguished as sweat glands and sebaceous glands, both arising in 

 connection with the hair follicles. Certain of the sweat glands on 

 the ventral surface are modified to form the mammary or milk glands, 

 from the presence of which the class receives its name. In all 

 save the lowest members of the class (Ornithorhynchus and 

 Echidna) the mammary glands open in groups on projections of 



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