674 PROFESSOR OWEN ON THE MARSUPIAL POUCHES, MAMMARY GLANDS, 
of the ventral integument, when a pouch or inverted fold of precisely similar shape, 
depth, and dimensions appeared, but with the opening turned the opposite way ; the 
folds were closer and less conspicuous on that side, the cavity of the pouch being flatter 
(see section, Plate XL. fig. 3), whence I inferred that the more open pouch (ib. section, 
fig. 2, c) had been the seat or nest of the very small and probably recently-born animal, 
whose position there, as in the figure, Plate XXXIX. a , had naturally led the original 
captor of the Echidna to conclude that it was hanging by a nipple. 
No such projection, however, presented itself in any part of the inner surface of either 
pouch ; but at the fundus of each was an “ areola ” or elliptic surface, about four lines 
in diameter (Plate XL. fig. 4), on which, with the pocket lens, could be discerned the 
orifices of about fifty ducts of a gland. The canals or roots of fine scattered hairs and 
several minute white papillae (ib. fig. 5,^?, p, magn.), about one or two lines apart, on 
which opened sebaceous follicles, were all the appearances characterizing the otherwise 
smooth and even surface of these inflexions of the abdominal integument. 
The contrast which this pouch presents with that of a true marsupial quadruped con- 
taining the mammary foetus* is great; for even in the uniparous species, e. g., the larger 
Kangaroos, two, if not four, long slender nipples are conspicuous, to one of which the 
foetus hangs, closely embracing the pendulous extremity of the nipple by its small, round, 
terminal, tubular mouth. 
My next step was to test the statement in reference to the number and condition of 
the mammary glands. 
I found, as in a former dissection of a younger unimpregnated female Echidnaf , that 
these glands were two in number, forming, like the pouches, a symmetrical pair (Plate 
XL. fig. 1). Each gland (a, a!) was of a flattened, subelliptic form ; the left (a) being 
1 inch 10| lines, the right (a!) 1 inch 8^ lines in long diameter, the left 1 inch 5 lines, 
the right 1 inch 3 lines in short diameter across the middle, and both glands about 5 
lines in thickness at the middle part (figs. 2, 3). Each gland consists of about 100 long, 
narrow, flattened lobes, obtusely rounded at their free ends, and beginning, at about half- 
way towards the opposite side, to contract gradually to the duct which penetrates the 
corium (Plate XL. figs. 2 & 3, 5), to terminate on the mammary areola (ib. c ) at the fun- 
dus of the pouch. From the small size of the areola compared with that of the gland, 
the lobules have a convergent arrangement thereto, each terminating in its own duct, 
without blending with the substance of a contiguous lobe ; and, as a general rule, with- 
out anastomosis of contiguous ducts to form a common canal. Each gland is enclosed 
in a loose capsule of cellular tissue (fig. 1, e, e) and lies between a thick “ panniculus car- 
nosus” (figs. 1, 2, 3, d, d 1 ), adherent to the abdominal integument (f,f) and the “ obli- 
quus externus abdominis ” muscle, on a plane exterior or “ lateral ” to the pouch. The 
glands had not been exposed or disturbed by any dissection in the preliminary examina- 
* For the signification of this term see “On the Generation of the Marsupial Animals,” Philosophical Trans- 
actions, vol. cxxiv. p. 333. 
f “On the Mammary Glands of the Ornithorhynchus ,” Phil. Trans., tom. cit. p. 537, PI. XYII. figs. 2 & 3. 
