44-0 Linruean Society. 



LTNNiEAN SOCIETY. 



May 4. — The reading of Mr. Morgan's paper On the mammary 

 organs of the kangaroo was continued, containing further particulars 

 of the dissection of these parts, as well as of the muscles attached 

 to the marsupial bones, in the adult and impregnated animal. 

 These bones, with their ligamentous and muscular connections, were 

 described, and several errors in Sir Everard Home's published ac- 

 count of these parts were pointed out. The author then stated his 

 own opinions respecting the use of these structures. He stated that 

 the marsupial bones are formed, 1st, for the purpose of giving that 

 firm support to the superincumbent abdominal viscera which the 

 narrow pelvis of the animal is incapable of affording while in the 

 erect posture ; and, 2ndly, for the purpose of constituting a fixed 

 point of resistance against which the mammae are squeezed by the 

 muscular girdle already described as inclosing those glands be- 

 tween their fibres. By this arrangement the female is enabled to 

 empty by compression the excretory ducts of its mammae, and thus 

 to force their secretions into the mouth of the imperfectly organized 

 young, which during the earlier periods of its existence appears in- 

 capable of extracting a nutritious fluid from that part by the usual 

 means. 



It appears that the secretion of this fluid (or milk) takes place 

 only in the larger and lower gland, and that its ejection through 

 the inferior and longer teat is assisted by a muscular investment 

 which incloses the ducts throughout their whole course from the gland 

 to the extremity of the nipple. The existence of this structure 

 has been noticed by M. Geoffroy St. Hilaire, who has assigned to 

 it the same use. Under this compressing muscle of the lower (or 

 as Mr. Morgan has named it, the true marsupial) teat, a congeries 

 of vessels which principally consisted of veins was described as form- 

 ing a plexus around the central fasciculus of ducts. These veins, 

 together with those of the gland, were stated to occasion a con- 

 siderable distention of the mammary organ during the time of suck- 

 ling, in consequence of the congestion which must necessarily oc- 

 cur in the vessels at that period, from the pressure made upon their 

 main trunks by the action of the compressing muscle of the mamma ; 

 for it has been found that the size of the organ on such occasions 

 exceeds that which a loaded state of the ducts only could produce. 

 The mammae were found, as in the virgin animal, to consist in dou- 

 ble glands on each side, the upper and smaller presenting the same 

 anatomical characters as in the former instance ; its excretory ducts, 

 however, in their course towards the upper nipple were found to be 

 inclosed in an indistinct muscular sheath, and there was a faint in- 

 dication of the existence of a plexus of vessels similar to that which 

 was found in the lower or true marsupial teat. This smaller mam- 

 mary organ is considered by the author as analogous to the super- 

 numerary mammae and teats of other mammiferous animals, since 

 the lower or true marsupial mammary glands and their teats ap- 

 pear to perform exclusively the office of preparing a nutritious 

 fluid for the support of the young animal. 



May 



