240 RODENTIA. 



The penis arises from, or is fixed in the common way to, the os pubis ; 

 but, after it has come forwards some way, it is immediately bent back 

 upon itself. The glans swells out to a considerable size, which termi- 

 nates all at once in a hollowed end, like the flower of a convolvulus, 

 in the centre of which is the opening of the urethra 1 . There is a short 

 bone in the glans. 



It has clavicles. The carpus and metacarpus are extremely short. 

 The ball of the thumb is very large and prominent : the ball of the 

 little finger is very prominent, though not so thick : the fingers are five ; 

 with the last joints long, with long nails. The tarsus and metatarsus 

 are long, as in the hare ; there are four toes, which are very strong, 

 the ends being covered by pretty broad strong nails. Below the outer 

 angle of the eye arise three whiskers : the face is like a hare's, but is 

 rather broader between the eyes. The two lips in the upper jaw unite 

 across the mouth, making a theca for the roots of the two fore-teeth in 

 the upper jaw. 



[Family JERBOIDJE.] 

 [The Jerboa (Dipus sagitta, Zimm.).] 



The Jumping Mouse. 



The stomach is globular, with the thick end very obtuse, small and 

 short. The duodenum passes to the right, and then down as low as 

 the pelvis, connected to the ascending part of the colon ; it then makes a 

 turn up to the left, behind the mesentery, and becomes loose. The 

 ileum passes into the caecum about the middle of the spine. The caecum is 

 about 4 inches long ; is large at the entrance of the ileum, becoming 

 smaller and smaller, ending in a point : it makes a turn, as it were sur- 

 rounding the entrance of the ileum in a spiral manner, with its small 

 end lying loose in the pelvis. 



The colon is largest at the beginning, makes a turn upwards, and is 

 attached to the first turn of the caecum by a mesocolon ; it passes a 

 little up on the right side, makes a fold upon itself about an inch and 

 a half ; and, when it crosses the spine, it makes another short fold ; 

 from thence it passes to the anus 2 . 



1 [There is a drawing of an animal in Sir Joseph Banks's library, called the jerboa 

 of Dr. Reinhold Forster, much like a jerboa, but much larger, and I think evidently 

 too small an animal to possess such a large penis. Vide No. 2497, gallery, marked 

 on the top of the bottle by Mr. Bell " Jerboa of Forster." (Now No. 2563.) When 

 Cuvier was in London (1818), he was much struck with the singular appearance of 

 this preparation, but did not know to what animal it belonged. — W. C] 



2 [Home, Comp. Anat. vol. i. p. 455 ( jumping mouse).] 



