CENTURY VIIT. 395 



ter 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 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, muscles, scallops, crabs, lobsters, 

 craw-fish, shrimps, and especially the tortoise, have 

 bones within them, but only little gristles. 



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. 



749. Most of the hard substances fly to the ex 

 tremes of the body : as skull, horns, teeth, nails, and 

 beaks : only the bones are more inward, and clad with 

 flesh. As for the entrails, they are all without bones ; 

 save that a bone is sometimes found in the heart of 

 a stag ; and it may be in some other creature. 



750. The skull hath brains, as a kind of marrow, 

 within it. The back-bone hath one kind of marrow, 

 which hath an affinity with the brain ; and other 

 bones of the body have another. The jaw-bones have 

 no marrow severed, but a little pulp of marrow dif 

 fused, Teeth likewise are thought to have a kind of 

 marrow diffused, which causeth the sense and pain ; 

 but it is rather sinew : for marrow hath no sense, no 

 more than blood. Horn is alike throughout ; and 

 so is the nail. 



