66 Mr. MongGaN's Description 
ence; but this aperture, minute as it appeared, exactly cor- 
responded with the extremity of the teat I have before re- 
ferred to as having been artificially everted; and further ex- 
aminations of various living Kangaroos, at different periods of | 
gestation, furnished proof that it is to this lower elongated. 
teat, and not to either of the upper nipples (which were found 
perfectly developed in the pouch of the unimpregnated Kan- 
garoo), that the young are invariably attached ; and from the 
period the young are first received into the pouch, to the time 
at which they become separated from the teat, the two supe- 
rior nipples, and the smaller mammary glands attached to them, 
perform no functions which can apparently be connected with 
the process of preparing a nutritious fluid for their support. 
It is also found, that the size and condition of the true teat 
are constantly changing, in proportion to the growth of the 
young to which it gives attachment; that as the young ani- 
mal increases in size, the teat enlarges; and this structure, 
—which in the. unimpregnated state will measure barely half 
an inch, and which at the time the young is first attached to 
it does not exceed the size of that which I had artificially - 
everted,—before the young has left the pouch, becomes en- 
larged and elongated to the extent of nearly six inches. The 
upper teats, however, remain in nearly the same condition as 
regards their relative size and form. —S every period 
of gestation. yat 
Repeated recent examinations of the living veram ES aio 
proved, that the lower teats, which for distinction I may term 
marsupial, invariably diminish, when the young animal has 
ceased to suckle, to a smaller size than even that which I had 
artificially produced by eversion; but that, after being once 
developed by protrusion from their original situation in the 
substance of the gland, they never again recede to their former 
condition, 
