"bum ENT 
of the Mammary Organs of the Kangaroo. 75 
The smaller gland appeared somewhat more vascular than 
that which I had before examined in the younger animal, and 
was connected by a similar arrangement of ducts with the upper 
and smaller nipple (tab. 8. f. 1.a.). From the larger marsupial 
mammary gland about twenty excretory ducts are sent off, these 
being closely connected together by reticular membrane, and 
inclosed in a sheath, (forming, as I have stated, a sort of fasci- 
culus or cord,) are continued to their termination at the extre- 
mity of the nipple in nearly a straight line. In its course from 
the gland, this plexus of ducts first passes between the skin of the 
pouch and the abdominal muscles as far as the base of the mar- 
supial teat, at which part it enters the teat, and is continued to its 
extremity, where each duct terminates by a separate opening. A 
sheath of longitudinal muscular fibres closely envelops this fas- 
ciculus of ducts throughout its whole extent; and at the point of 
junction with the gland, these muscular fibres are expanded over 
the surface of that organ, to nearly the whole of which they are 
attached by cellular connections (tab. 8. f. 1. 5.). < 
The use of this muscle is to draw up and shorten the teat, when 
its ducts are emptied, or to compress that part when this retrac- 
tion is prevented by a distended state of its vessels: whenever, 
therefore, the lactiferous tubes are filled by injection from the 
mammary gland, and the part becomes distended, this muscle 
considerably facilitates the transmission of the secreted fluid 
through the teat by compressing the ducts, and thus squeezing 
their contents towards the extremity of the nipple. ‘Thus the 
lactiferous tubes within the mammary gland, and the excretory 
vessels which are sent off from those tubes through the teat, are 
furnished by Nature with precisely the same muscular apparatus 
for the ejection of their contents. 
The compressing muscle of the teat, however, is only capable 
of performing this office when assisted by that of the gland; for 
L 2 until 
