of young Marsupial Animals. 189 
rated as the young animal grows, when the muscular 
system is more developed, and when it is able to assist 
by its own efforts in holding and sucking. The attach¬ 
ment of the young to the teat is almost mechanical, but 
not quite ; the little additional force required to close the 
opening is possessed by the young one, and it hangs 
and moves, not by its own exertions, but by the action 
of the muscle I have before spoken of spread upon the 
mammary gland. 
There is another point connected with the history of 
the young of marsupial animals which is of interest. 
In 1834 a female cat had been shot, and was brought to 
me, with some young ones in the pouch; the young had 
been born about a fortnight—the eyes unclosed, the lips 
not formed: on separating them from the teat, they readily 
regained it, and remained attached, although the mother 
had been dead some hours. I was desirous of preserving 
these young animals for future observations, and for that 
purpose I placed them in some strong spirits in a closed 
glass jar: but the following day they were still living, 
and moved almost as quickly as they did before their im¬ 
mersion. On another occasion I had a dead kangaroo rat 
brought with a living young one in the pouch. Not wishing 
to keep this one living in misery so long, I divided all the 
large vessels about the neck : this not killing it, 1 pithed it 
between the atlas and occiput. But as it still moved, I 
removed the head ; the body still, by free motions on the 
application of irritants, shewed sensibility : in half an 
hour I opened the body to examine it, and the creature 
still moved slightly. 
These facts present some interesting points of enquiry 
connected with the physiology of the nervous system 
and respiration ; particularly the irritability in the young, 
being nearly allied to the irritability of cold-blooded ani¬ 
mals, and connected with a corresponding tenacity of life. 
