COMPARATIVE ANATOMY. 
interesting phenomena in the whole eirele 
of comparative anatomy. Physiologists 
have not yet ascertained, whether the em- 
bryo possesses, at any period, a connection 
with the uterus similar to that which is 
observed in the other mammalia: but it 
appears veiy probable, that the processes, 
which follow the passage of the ovum from 
the oyarium, are entirely different in these 
animals, from those which take place in the 
other mammalia. Neither has the precise 
period, at which the foetus enters tire false 
belly been hitherto shewn. 
The following statement of the subject, 
as far as it is at present known, is derived 
from Mr. Home’s paper. (Phil. Trans. 
1795 .) 
The uterus and lateral canals, in their 
pregnant state, are distended with a very 
adhesive jelly of a bluish white colour ; 
which also fills the oval enlargements of 
the Fallopian tubes. 
“ In the cavity of the uterus,” says Mr. 
Home, “ I detected a substance which ap- 
peared organized ; it was enveloped in the 
gelatinous matter, and so small as to make 
it difficult to form a judgment respecting 
it ; but when compared with the foetus after 
it becomes attached to the nipple, it so 
exactly resembled the backbone with the 
posterior part of the skull, that it is readily 
recognized to be the same parts in an ear- 
lier stage of their formation.” 
This substance has been represented in 
a plate ; but the engraving does not, in 
our opinion, possess the slightest similitude 
to the parts mentioned by Mr. Home. 
The size of the foetus at the time it leaves 
the uterus is not yet ascertained. The 
smallest, which has been hitherto found in 
the false belly, weighed twenty-one grains ; 
and was less than an inch in length. In 
another instance it was “ thirty-one grains 
in weight from a mother of fifty-six pounds. 
In this instance the nipple was so short a 
way in the mouth, that it readily dropped 
out, we must therefore conclude that it had 
been very recently attached to it. 
“ The foetus at this period had no navel 
string, nor any remains of there ever hav- 
ing been one ; it could not be said to be 
perfectly formed, but those parts which 
fit it to lay hold of the nipple were more so 
than tlie rest of the body. The mouth was 
a round hole, just enough to receive the 
point of the nipple; the two fore-paws, 
when compared to the rest of the body, 
were large and strong, the little claws ex- 
tremely distinct ; while the hind-legs, wliich 
are afterwards to be so very large, were 
botli shorter and smaller than the fore ones.” 
“ The mode in which tlie young kanguroo 
passes from the uterus into the false belly, 
has been matter of much speculation ; and 
it has even been supposed that there was 
an internal communication between these 
cavities ; but after the most diligent search, 
I think I may venture to assert that there 
is no such passage. This idea took its rise 
from there being no visible opening be- 
tween the uterus and vagina in the unim- 
pregnated state ; but such an opening being 
very apparent, both during pregnancy and 
after parturition, overturns this hypothesis ; 
for we cannot suppose that the foetus, when 
it has reached the vagina, can pass out in 
any other way than through the external 
part.” This passage will be facilitated by 
the power which the animal possesses of 
drawing down the false belly to the vulva, 
which has naturally a considerable projec- 
tion. 
The female organs of generation of birds 
consist of an ovarium, and an oviduct, 
which opens into the cloaca. Its aperture 
is placed towards the left of that organ. 
The tube itself is convoluted, somewhat like 
an intestine. Its inner coat is furnished 
witli numerous papillae. Its diameter is 
tlie most considerable at the cloaca, from 
which it gradually diminishes. It opens 
towai'ds the abdomen by an expanded ori- 
fice, called the infundibulum ; which is ana- 
logous to the fimbriated orifice of the Fal- 
lopian tube. 
The ovarium, resembling in its appear- 
ance a bunch of grapes, lies under the liver, 
and contains in a young laying hen about 
five hundred yolks, varying in size from a 
pin’s head, to their perfect magnitude : the 
largest always occupy the external circum- 
ference of the part. Each yolk is inclosed 
in a membrane (calyx) which is joined to 
the ovarium by means of a short stalk or 
pedicle (petiolus.) A white shining line 
forms on the calyx when the yolk has at- 
tained its complete magnitude. The mem. 
brane bursting in this part, the contained 
yolk escapes, and is taken up by the infun- 
dibulum in a manner which we cannot ea- 
sily conceive. It then passes along tire 
oviduct, and acquires in its passage the 
white and shell. The calyx, on the con- 
trary, remains connected to the Ovarium ; 
but it contracts and diminishes in size, so 
that in old hens, which have done laying, 
the whole internal organs of generation 
nearly disappear. 
