718 



MAMMALIA. 



/A 



tenance therefrom by its own unaided efforts. The mother, as 

 Professor Geoffroy* and Mr. Morgan -f* have shown, is therefore 

 provided with a peculiar adaptation of a muscle (analogous to the 

 cremaster) to the mammary gland, for the evident purpose of in- 

 jecting the milk from the nipple into the mouth of the adherent 

 fetus. Now it can scarcely be supposed that the fetal efforts of 

 suction should always be coincident with the maternal act of injec- 

 tion ; and, if at any time this should not be the case, a fatal acci- 

 dent might happen from the milk being forcibly injected into the 

 larynx. Professor Geoffroy first described the modification by 

 which this purpose is effected, and Mr. Hunter appears to have 

 foreseen the necessity for such a structure, for he has dissected 

 two small fetuses of the Kangaroo for the especial purpose of 

 showing the relation of the larynx to the posterior nares. J The 

 epiglottis and arytenoid cartilages are elongated and approximated, 

 so that the rima glottidis is thus situated at the apex of a cone- 

 shaped larynx (Jig. 331, B, a), which projects, as in the CE- 

 TACEA, into the posterior nares, Fig. 331. 



where it is closely embraced by the 

 muscles of the soft palate. The air- 

 passage is thus completely separated 

 from the fauces, and the injected 

 milk passes in a divided stream, on 

 either side of the larynx, into the 

 oesophagus." 



" Thus aided and protected by 

 modifications of structure, both in 

 the system of the mother and in its 

 own, designed with especial refer- 

 ence to each other's peculiar condi- 

 tion, and affording therefore the 



most irrefragable evidence of creative foresight, the feeble off- 

 spring continues to increase from sustenance, exclusively derived 

 from the mother, for a period of about eight months. The young 

 Kangaroo may then be seen frequently to protrude its head from 

 the mouth of the pouch, and to crop the grass at the same time 



* Memoires du Muse~e, torn. xxv. p. 48. .f Trans. Lin. Society, vol. xvi. p. 61. 



t " See Nos. 3731, 3734, 3735, in the Physiological series of the Hunterian Mu- 

 seum, in which there are evidences that Mr. Hunter had anticipated most of the 

 anatomical discoveries which have subsequently been made upon the embryo of the 

 Kangaroo." 



