772 



ANATOMY OF VERTEBRATES. 



606 



from the uterus to the pouch : — the mouth of the vagina cannot 

 be brought into contact with that of the pouch, either by mus- 

 cular contraction in the living or by any force of stretching in 

 the dead Kangaroo :— as the young was proved by the result of 

 this experiment not to have the power of itself to regain the 

 nipple, a fortiori we may conclude that it could not transfer itself 

 from the vulva to the interior of the pouch and to the apex of the 

 nipple : — the fore-paws of the Kangaroo would not so effectually 

 protect the tender embryo from the external air as the mouth, 

 nor so safely ensure its passage to the pouch, notwithstanding 

 that they are adroitly used in grasping objects, being similar, in 

 respect of the extent and freedom of motion of the digits, to the 

 fore-paws of the Rodents. 



The new-born Kangaroo (Macrojms major, fig. 606), which I 

 discovered in the pouch a few hours after uterine gestation, 

 measured one inch from the mouth to the 

 root of the tail, was quite naked, and covered 

 by a thin semitransparent vascular integu- 

 ment ; the place of attachment of the umbi- 

 lical chord was obscurely indicated by a 

 longitudinal linear cicatrix. The fore-legs 

 were longer and stronger than the hind ones, 

 and the digits were provided with claws ; 

 the toes were developed on the hind-legs ; 

 the body was bent forward ; and the short 

 tail tucked in between the hind-legs. This little animal breathed 

 strongly, but slowly : no direct act of sucking could be perceived. 

 Such, after a gestation of thirty-eight days, is the condition of 

 the new-born young of a species of Kangaroo, of which the adult, 

 when standing erect on his hind-feet and tail, can reach to the 

 height of seven feet. 



It has greater powers of action than the same sized embryo of 

 the sheep ; but less than has the new-born young of the rat. 

 For, although it is enabled by the muscular powers of the ' orbi- 

 cularis oris,' and those of the precociously-developed tongue, to 

 grasp and adhere firmly to the nipple, it seems unable to draw all 

 the needed sustenance therefrom unaided. And here the modified 

 ( cremaster' comes into play, being adapted to inject the milk into 

 the small feeble prematurely-born creature's mouth. One cannot 

 suppose that its efforts at suction should always and exactly 

 coincide with the mother's act of injection. And we find, in 

 fact, provision for the required special relation of the larynx to 

 the posterior nares. The epiglottis and arytenoid cartilages are 



New-born foetus and left nipples, 

 Macropus major. 



