32 NATURAL HISTORY. 



of the teeth deserveth to be inquired of, as well as 

 the other parts of living creatures bodies. 



747. There be five parts in the bodies of living 

 creatures, that are of hard substance ; the skull, the 

 teeth, the bones, the horns, and the nails. The great- 

 est quantity of hard substance continued is towards the 

 head. For there is the skull, of one entire bone ; there 

 are the teeth ; there are the maxillary bones ; there is 

 the hard bone that is the instrument of hearing ; and 

 thence issue the horns ; so that the building of living 

 creatures bodies is like the building of a timber house ; 

 where the walls and other parts have columns and 

 beams, but the roof is, in the better sort of houses, all 

 tile or lead or stone. As for birds, they have three 

 other hard substances proper to them ; the bill, which 

 is of the like matter with the teeth ; for no birds have 

 teeth : the shell of the egg : and their quills : for as 

 for their spur, it is but a nail. But no living creatures 

 that have shells very hard (as oysters, cockles, mussles, 

 scallops, crabs, lobsters, era-fish, shrimps, and espe 

 cially the tortoise,) have bones within them, but only 

 little gristles. 1 



748. Bones, after full growth, continue at a stay ; 

 and so doth the skull : horns, in some creatures, are 

 cast and renewed : teeth stand at a stay, except their 

 wearing: as for nails, they grow continually: and bills 

 and beaks will overgrow, and sometimes be cast ; as in 

 eagles and parrots. 2 



1 Here, as in 732., we see that Bacon knew but little of the natural his 

 tory of the tortoise. 



2 Bones, like the soft parts of the body, are renewed throughout life, and 

 so in many cases are teeth. Cuvier has remarked that the mutual adapta 

 tion of teeth and the bones with which they are connected is one of the 



