LEPUS TIM1DUS. 199 



This order of animals consists of many genera, each of which contains 

 several species, and many species have considerable varieties. 



I shall give the genera in the order of size [beginning with the 

 largest] : — le cabiai, la paca, beaver, porcupine, hare, rabbit, guinea-pig, 

 jerboa, mouse. 



Of the Teeth. — The four front teeth of this order are continually 

 growing; and, if broken at any time, they grow again to their full 

 length 1 ; and are formed at their extremities by their action upon one 

 another into their chisel form, as perfect as at the first. They never 

 close or contract at their [base, or] growing extremity, as in those 

 animals in which the teeth have a limited time for growing ; but are 

 always open, at the [basal] end, like a socket filled with a jelly, as in 

 all other growing teeth. The way of life of the animal shows that 

 something of this kind is necessary, as these animals use their teeth 

 wholly in cutting or separating their food from its attachments, as in 

 taking off bark, &c. : they likewise use their teeth in other common 

 purposes of rife, such as dividing parts that are in their way, or working 

 their way through wood, brick, stones, <fcc, and making free communi- 

 cation everywhere. 



[Family LEPORID^E.] 

 The Hare \_Lepus timidus, Linn.] 2 . 



The oesophagus at the lower part of the thorax, before it goes through 

 the diaphragm, passes into a capsule, which allows it at this part to be 

 unattached all round excepting at the posterior part, where it is attached 

 all along to the posterior mediastinum. This capsule is attached to, or 

 may be said to be made up (upon the left) of, the posterior mediastinum, 

 and of two membranes going from the fourth and fifth lobes of the lungs 

 of the right side, to be fixed to the posterior mediastinum : the mem- 

 brane from the fifth lobe passes before the oesophagus, that from the 

 fourth behind, and is attached to the posterior mediastinum by a thin 

 membrane or meso-cesophagus. 



The oesophagus is about an inch long below the diaphragm, at least 

 at its fore-part. The stomach is roundish, not oblong, making a pretty 

 quick turn or curve : the oesophagus is inserted nearer to the great end 

 than to the pylorus : the great end of the stomach is turned up, and 

 adheres to the left of the oesophagus for nearly one quarter of an inch. 



1 [In a coypu at the London Zoological Gardens, that had broken an inch off the 

 left lower incisor, I observed (in 1835) that it grew up to its ordinary length in six 

 weeks.] 



2 [The osteology of the hare is shown in the Hunterian specimens Nos. 1916 — 1928.] 



