of the Mammary Organs of the Kangaroo. 73 



muscular contraction for the purpose of compressing a gland, 

 and thereby emptying its ducts of their contents, we have 

 already sufficient proof. The venom of the Rattle-snake is 

 forced through its perforated fang by a muscular apparatus 

 connected with the secreting organs ; and the musk gland of 

 the Crocodile has been shown by my friend Mr. Bell* to pos- 

 sess a muscular investment, obviously destined to perform the 

 same functions as T have attributed to a similar peculiarity of 

 structure in the Kangaroo. 



The use of a forcible compression of the mammary gland of 

 the Kangaroo, exerted at the will of the mother for the purpose 

 of ejecting its secretion, will be rendered apparent by an ex- 

 amination of the young at the time it is first attached to the 

 nipple ; for the imperfect state of organization in which we find 

 the young of marsupial animals at the time they first make their 

 appearance in the pouch, — more particularly evinced by the 

 state of the mouth and its appendages, — compared with the 

 more mature development of the same parts in the young of 

 other mammalia, renders some provision necessary, by which 

 nutrition should be imparted solely by the agency of the mother ; 

 and this provision is clearly afforded by the injection of the 

 milk into the mouth by the means I have already mentioned, 

 instead of that fluid being extracted by the suction of the young, 

 as in the case of other mammiferous animals. That the secretion 

 of the marsupial mammary gland may be ejected by pressure 

 made upon the part, is rendered probable not only by the exist- 

 ence of a compressing muscle, but also by the structure of the 

 marsupial teat and its proper investments, which I shall next 

 describe. I wish it, however, to be clearly understood, that in 

 the description which I am now giving of the anatomy of these 

 parts, I refer to the mammary organ in the full-grown Kan- 



* Phil. Trans. 1827, j). 132. «. 11. 



VOL. XVI. L garoo. 



