870 



PHYLUM CHORDATA : CLASS MAMMALIA 



The stomach is always simple ; the caecum is absent, or 

 short, or simple ; the colon is not sacculated. 



There are no vesiculae seminales. The uterus is bicor- 

 nuate. The mammae are abdominal. The placenta is 

 deciduate and zonary. 



Representatives of Carnivora are found in all parts of the 

 world. 



The true Carnivores are for the most part terrestrial. The incisors 

 are almost always ^, the canines are usually large ; one of the 

 back teeth is modified as a trenchant carnassial or sectorial. 

 The digits generally have sharp claws, which may be retractile. 



GBR 



MO 



Fig. 517. —Side view of the brain of a dog. 



CBR., Convoluted cerebral hemispheres ; CBL., transversely 

 grooved cerebellum ; O.L., olfactory lobe ; O.N., optic nerve 

 cut short ; P., pituitary body ; M.O., medulla oblongata 

 below the cerebellum ; S.C., spinal cord. The roots of 

 various nerves are seen arising from the medulla and the 

 spinal cord. 



Within the sub-order there are three sections — /Eluroidea 

 Cynoidea, and Arctoidea — represented respectively by cat, 

 dog, and bear, but these types are connected by extinct 

 forms. 

 In retractile claws, the last phalanx of the digit with its attached 

 claw is drawn back into a sheath on the outer side of the middle 

 phalanx in the fore-foot, on the upper side in the hind-foot. When 

 the animal is at rest or is walking, the claw is retained in this bent 

 position by an elastic ligament, and is in this way protected from 

 wear. When the animal straightens the phalanges, the claws are 

 protruded. 



Digitigrade animals walk on their toes only ; plantigrade forms rest 

 the whole sole of the foot on the ground ; but between these conditions 

 there are all possible gradations. Many Carnivores are sub-plantigrade, 

 often when at rest applying the whole of the sole to the ground, but 

 keeping the heel raised to a greater or less extent when walking. 



