BOOK XI. Lxiv. 169-LXV. 172 



family likewise looses teeth when two-and-a-half 

 years old, and again six months later ; tliose that 

 have not foaled before they shed their last teeth 

 are sm*e to be barren." Oxen change their teeth 

 at the age of two. Pigs never shed theirs.* 



When this indication has come to an end, old age 

 in horses and other beasts of bm-den is inferred from 

 prominence of the teeth and greyness of tlie brows 

 and hollows round them, when they are judged to be 

 about sixteen years old. 



Human teeth contain a kind of poison, for they oiherfacu 

 dim the brightness of a mirror when bared in front 

 of it and also kill the fledgUngs of pigeons. The 

 rest of the facts about the teeth have been told in 

 the passage ^" dealing with human reproduction. 

 Infants when cutting their teeth are specially Uable 

 to iUnesses. The animals with serrated teeth have 

 the severest pain in teething.'* 



LXV. Not aU species have tongues on the same Theton^ 

 plan. With snakes the tongue is extremely slender 

 and three-forked, darting, black in colour, and if 

 dra>\Ti out to fuU length extremely long ; with 

 Uzards it is cleft in two and hairy, and with seals also 

 it is double ; but with the species above mentioned 

 it is of the fineness of a hair. With the rest it is 

 available for Ucking round the jaws, but with fish it 

 adheres through a Uttle less than its whole length, 

 and with crocodiles the whole of it. In aquatic 

 species on the other hand the fleshy palate serves 

 instead of the tongue in tasting. With Uons, 

 leopards, and all the species of that genus, even 

 cats, the tongue is rough and corrugated Uke a file, 

 and can scrape away the human skin by Ucking, 

 which provokes even those that have been tamed 



539 



