376 Linncean Society. 



of these parts, both in the virgin and in the impregnated animal ; to- 

 gether with the author's opinions respecting the physiology of certain 

 structures which have been hitherto unnoticed, and of others which 

 have been incorrectly or imperfectly described by former investigators 

 of this interesting branch of natural science. 



The author first pointed out the anatomical peculiarities which he 

 had discovered in a dissection of the pouch and mammae of a young 

 and unimpregnated kangaroo ; by which it appears, that, in the virgin 

 state, the two upper nipples only are found to be developed, and that 

 beneath each of these a minute circular aperture, resembling in ap- 

 pearance the mouth of a follicle, occupies the exact situation in which 

 the lower teat is known to exist in the adult impregnated animal. — 

 The mammae are described as consisting of double glandular struc- 

 tures on each side ; they are situated directly behind the follicular 

 openings already mentioned, and are closely confined to the posterior 

 surface of the integuments. Each double mamma is formed by an 

 upper and smaller gland, which is attached by its excretory ducts to 

 the already developed nipple, and by a second and larger glandular 

 substance from which no excretory duct could be traced. The folli- 

 cular apertures which occupy in the pouch the situation of the lower 

 teats, form the external openings of cylindrical membranous canals 

 which lie imbedded in the substance of the larger and lower mam- 

 mary glands. Each of these membranous canals or tubes is about 

 three-fourths of an inch in length, and extends through nearly the 

 whole diameter of the larger gland which encloses it ; the interior of 

 the tube is lined by cuticle, and the internal extremity is terminated 

 by a rounded papilla which projects into its cavity. 



In these papillae the author found a perfect miniature resemblance 

 to the extremities of the lower teats in the adult animal, which teats 

 he considers to be formed, during the first gestation, by the complete 

 eversion of the membranous canals, and the consequent projection of 

 their papillary terminations. He further states, that by artificially 

 everting the parts, two perfect teats are produced in the precise situa- 

 tion of those which are found in after life. It has been however as- 

 certained that this extraordinary change occurs only during the first 

 gestation, since after being once developed the teat remains perma- 

 nently formed and projected. 



Having thus described the condition of the mammary glands and 

 the development of the lower teats in the virgin animal, the author 

 gave a particular account of his dissection of an adult female, which 

 at the time of death was suckling a young one nearly half-grown. 

 In this we are informed that the panniculus carnosus which covers 

 the anterior surface of the belly is of extraordinary thickness, and 

 composed principally of perpendicular muscular fibres, which in their 

 course from the thorax downwards surround the mouth of the pouch 

 to which they form a sphincter muscle, and that a fasciculus of its 

 fibres descending over the symphysis pubis is inserted into the sphinc- 

 ter muscle of the cloaca ; so that the contraction of this part of the 

 panniculus carnosus would powerfully operate in approximating the 

 external aperture of the vagina with the mouth of the pouch. 



On 



