of the Mammary Organs of the Kangaroo. TT 
the pouch in the living animal, that it is produced at will by the 
mother, apparently for the purpose of preparing the parts for 
the more ready transmission of milk to the young. On. these 
occasions the gland and teat will be found of nearly double the 
size which a full injectment of the ducts is capable of producing. 
The cause of this additional enlargement however was, as I 
conceive, explained by an examination of the vascular system in 
the parts alluded to ; for by continuing the dissection, and care- 
fully removing the compressing muscles of the gland and teat, 
it was found that, from the number and size of the veins, any 
obstrüction to the circulation of blood through these vessels 
would in itself be sufficient to occasion a degree of distention by 
Which the extraordinary increase of size in these parts might be 
adequately accounted for. The distribution of the veins in the 
marsupial gland is not characterized by any remarkable appear- 
ance as regards their course; from their immense number, 
however, the whole surface of the gland presents when closely 
examined a reticulated congeries of vessels, which, with those of 
the interior, unite into larger trunks, the greater number of which 
terminate on the outer convex surface of the gland in a single 
vessel (żab. 8. f. 2. a.), which passes first between the two layers 
of the proper muscle of the mamme, afterwards descends upon 
the tendon of the external oblique, and ultimately empties itself 
into the external iliac vein. ‘This vessel, however, conveys only 
a part of the blood from the marsupial gland towards the heart, 
since another venous trunk, issuing from the inner margin of the 
gland, descends in a similar manner to the same termination, 
namely, to the iliac vessels. This vein conveys not only the 
remaining portion of blood from the gland, but also the whole 
of that which returns from the marsupial teat (tab. 8. f. 2. b.). 
Venous circulation, carried on through vessels thus situated, 
must necessarily meet with obstruction from the action of the 
compressing 
