NATURAL HISTORY. 2L 



Hope humbly then ; with trembling pinions soar ; 

 Wait the great teacher Death, and God adore.&quot; POPE. 



54. WHiy are persons remarkable for their stupidity commonly 

 termed &quot; thick-headed ?&quot; 



The bones of the cranium which are in connection with those of 

 the face, require to increase proportionately in their growth, so as to 

 keep pace with the face, and preserve the symmetry of the parts. 

 This they do, however, only in their external table, the internal 

 remaining to preserve the symmetry of the bones of the cranium. 

 From this inequality of development, spaces are left between the two 

 tables termed sinuses. In the forehead, immediately under the eye 

 brows, there are two such named frontal sinuses. It sometimes 

 happens that the brain shrinks from disease, as in idiocy. In such 

 cases the internal table follows the brain, and the distance between 

 the two tables is increased, the intervening space being either 

 filled with a kind of refuse, or remaining empty, forming unusually 

 large sinuses. 



55. A female child about four months after birth was noticed to have an unusually 

 large head. Till the fourth year, however, it did not excite much attention, and 

 the mental powers up to this period seemed to be excited in the ordinary degree. 

 At this period, however, the head began rapidly to enlargo, and the ro ind became 

 more and more obscured, till complete idiocy supervened, and continued till Her 

 death, which occurred in her twenty-second year. The head became too large to be 

 supported by the puny muscles of the neck ; she therefore constantly lay on a pallet 

 by the side of the fire. She appeared to have some slight glimmerings of mind, was 

 readily amused, like a young child, with noise and brilliant objects, and for years 

 kept rubbing a penny piece in her hands, which she would not part with day or 

 night, and which became at length reduced to the thinness of a wafer. 



56. What purposes are served by the projection of the heel and 

 the prominence of the knee-pan ? 



They increase by mechanical adjustment the power of the muscles ; 

 for by such means the point of insertion of the muscles is removed 

 to a distance from the centre of motion in the joint, and the lever 

 power thus obtained is greatly increased. 



57. Why is it, that although the bones are designed for the strength 

 ening and support of the frame, yet ihey never touch each other ? 



Because were it not for the fine elastic material, the cartilage, 

 interposed between the bones, the frame would be deprived Of its 



