INSECTIVOROUS MAMMALIA. 363 



fording an extensive surface of attachment for the large pec- 

 toral muscles, from which the limb derives its principal 

 force. The head terminates in front by a pointed nOvSe, 

 which is armed at its extremity with a small bone, intended 

 to assist in penetrating through the ground. 



While all this attention has been paid to the development 

 of the anterior part of the body to which these instruments 

 specially contrived for burrowing are affixed, the hinder 

 part is comparatively feeble, and appears stinted in its 

 growth, and curtailed of its fair proportions. The pelvis is 

 exceedingly diminutive, being reduced to a slender sacrum; 

 and it is thrown far back from the abdomen, to which it 

 could give no effectual protection. Hence the animal, when 

 above ground, w^alks very awkwardlj^, and is unable to ad- 

 vance but by an irregular and vacillating pace.* 



We have seen that there is a tribe of fishes armed ex- 

 ternally with sharp spines, which they are capable of erect- 

 ing when in danger of attack. A similar kind of defensive 

 armour is furnished to the Porcupine and the Hedgehog, 

 which belong to the family of insectivorous quadrupeds. 

 For the purpose of erecting these bristles, when the animal 

 is irritated or alarmed, there is provided a peculiar set of 

 muscular bands, which forms part of the usual subcutaneous 

 layer, termed the pannicidus carnosus. In the hedgehog 

 these muscles are very complicated, and give the animal 

 the power of rolling itself into a ball. A minute descrip- 

 tion of these muscles has been given by Cuvier, who found 

 that the whole body is enveloped in a large muscular bag, 

 or mantle, lying immediately under the integuments; and 

 capable, by the contraction of different portions of its fibres, 

 of carrying the skin over a great extent of surface. In the 

 usual state of the animal, this broad muscle appears on the 



* The only quadrupeds which resemble the mole in the perfect adaptation 

 of their structure to the pui-poses of burrowing", are the Wombat and the 

 Koala, which are among" the many extraordinary animals inhabiting- the con- 

 tinent of Australia. Their hind leg's are constructed in a manner vei'y mucli 

 resembling- the human fore-arm. (See Home, Lectures, See. i. 134.) 



