BOOK XI. Lxxxvii. 215-LXXXV111, 218 



the animals that do not get fat have hard bones; 

 those of asses are resonant enough to use as flutes. 

 Dolphins being viviparous have bones and not spines, 

 but snakes have spines. Soft aquatic species have no 

 bones, but rings of flesh bound round the body, for 

 instance the two kinds of cuttle-fish. Insects also 

 are said to be equally devoid of bones. The gristly 

 aquatic species have marrow in the spine, and seals 

 have gristle, not bones. Similarly with all that have 

 ears and nostrils that just project these are soft and 

 flexible, nature thus insuring them against fracture. 

 \Vhen gristle is burst it does not join up, and when 

 bones are amputated they do not grow again, except 

 the bone between the hoof and the hock in beasts of 

 burden. Human beings grow taller to the age of 

 twenty-one and from then onward fill out ; but more 

 particularly at the period of puberty they are noticed 

 to get free from a sort of impediment to their growth, 

 and especially so in sickness. 



LXXXVIII. The sinews starting from the heart, ^^^ *»»««'»• 

 and in the ox actually wrapped round the heart, 

 have a similar natm-e and explanation, being in all 

 animals attached to the slippery bones and binding 

 together the links of the bodily frame called joints, 

 in some cases by coming between them, in others by 

 surrounding them and in others by passing from one 

 to another, being at one point rounded and at another 

 flattened as the conformation of the joint requires 

 in each case. The sinews also do not join again if cut, 

 and, what is surprising, though extremely painful if 

 wounded cause no pain at all if cut through. Some 

 animals, for instance fishes, have no sinews, as they 

 are held together by their arteries ; although the 

 soft species " of the fish genus lack arteries as well. 



569 



