234 RODENTIA. 



hole into the side of it, and blowing into it, no air escapes by the side 

 of the opening of the Fallopian tube into the capsule. The ovary is 

 like a cluster of yolks in the hen. 



They produce ten or twelve young ones at each gestation. They 

 have a placenta to each, which is attached to that side of the uterus 

 where the meso-uterus [peritoneal fold attached to the cornu] is, or 

 where the vessels enter that tube. There appears to be no spongy 

 chorion going out from, the edge of the placenta to cover the foetus. 

 The membranes come out from the root of the umbilical chord 1 . 



There are twelve nipples, six on each side, three of which are on the 

 abdomen, and the other three on the thorax. 



Of the Common Mouse \_Mus musculus, Linn. 2 ]. 



This animal comes nearest to the rat in external form of all that I 

 know of this order ; yet it is a very different kind of animal : its food 

 may be said to be different, as mice eat little but what is of the vege- 

 table kind. Cheese may be said to be its principal animal food: 

 however, mice will eat dried animal food. 



It differs from the rat in having but five nipples 3 . 



Mice, like cats, bitches, &c, carry off their young when disturbed. 

 In a meadow when the grass was mowed, a mouse-nest was found with 

 young ones in it : next morning, when the mowers were going to take 

 the nest with the young, the young were gone. They were too young 

 to have gone of themselves, and indeed it was not to be supposed ; for 

 they had not been disturbed themselves ; the nest having been left 

 entire 4 . 



i [Hunt. Preps. Nos. 3466—3468.] 



2 [The skeleton is No. 2238, Osteol. Series.] 



3 [The usual number of nipples in the Mus musculus is eight ; and they sometimes 

 produce as many young. Daubenton states that, of eight gravid mice which he 

 dissected during the months of February, April, May, June, and November, one had 

 four young, four had each five young, two had each six young, and one had eight 

 young. He notices several varieties in the number of the nipples in the black rat, 

 the ordinary number being ten, six ventral and four pectoral ; but " some individuals 

 have supernumerary nipples, whilst in others the ordinary number is not complete." 

 Hunter may have observed a variety, by defect, in this respect, in the common 

 mouse. See Buffon, Hist. Nat. 4to. torn. vii. p. 279.] 



* ["I have seen the same thing in the domestic mouse." — W. Clift, 1821.] 



