MARSUPIALIA. 
nandez and Maffeius respecting the function of 
the marsupial pouch; “ for,” says Tyson, 
“here I find they place the mammez or teats, 
and they tell very odd stories about it,” &c. 
The female Opossum which Tyson dissected 
appears to have been a young one, and there- 
fore, for a reason which has lately been clearly 
explained by Mr. Morgan, he was unable to 
detect thenipples within the pouch, and although 
he confesses that he was equally unable to find 
them upon the outer skin, he rejected the state- 
ments respecting the premature birth of the 
young and their pendulous attachment to the 
nipple, and, believing the generation of the 
Opossum not to deviate from that of ordinary 
quadrupeds, he limited the function of the 
marsupium to that of affording a temporary 
shelter to the young in time of danger. 
assertions of Hernandez and Maffeius 
were soon, however, corroborated by other ob- 
servers; and Daubenton* repeated and con- 
firmed the dissections of Tyson, so far as re- 
garded the existence and general form of the 
uterus; but no satisfactory explanation was 
offered as to the nature or precise period of the 
uterine development or of the passage of the 
young to the marsupium. 
The next really important advance towards 
the solution of this problem was made by 
John Hunter, who in the dissection of some 
marsupial foetuses of the Kangaroo detected 
evidences of a deviation from the ordinary 
mode of mammiferous development, fn the ab- 
sence of the usual traces of a placental organi- 
zation ; there being in these fetuses no per- 
ceptible remains either of an urachus, of umbi- 
lical arteries, or of an umbilical vein. The 
beautiful series of preparations+ exhibiting these 
and other interesting facts in the structure of 
the mammary t foetus of the Kangaroo are pre- 
served in the Museum of the Royal College of 
Surgeons, and afforded the principal materials 
for the paper on Marsupial Generation, pub- 
lished by Mr. (afterwards Sir Everard) Home, 
in the 85th vol. of the Philosophical-Transac- 
tions (1795). I have already shewn that one 
of the chief grounds of the theory of marsupial 
generation there | agree is untenable, the sup- 
posed remains of the foetus,§ described as being 
situated in the corpus uteri, (vaginal cul-de-sac,) 
being nothing more than a portion of the inspis- 
sated secretion commonly present both in this 
sac and the lateral canals. The temporary ori- 
fice by which the fcetus is stated to pass imme- 
diately from the so called corpus uteri into the 
vagina (uro-genital passage) does not exist. 
In the subsequent theory of marsupial gene- 
* Buffon, Hist. Naturelle, vol. x. 
+ See Nos. 3758-3777, Physiol. Catal. vol. v. 
¢ I adopt this termfrom M. de Blainville, in 
preference to the term ‘ marsupial’ previously pro- 
posed by Dr. Barton, to express the condition of the 
young of the Marsupialia from the time they enter 
the pouch to that of quitting the nipple, or to the 
close of the period of their uninterrupted attach- 
ment to the nipple. 
§ No. 3460 F. Physiol. Series, Mus, R. Coll. 
of Surgeons, 
319 
ration propounded by Sir Everard Home,* the 
‘ cornua uteri’ of Tyson are regarded as por- 
tions of the Fallopian tubes. These he believes 
to furnish the yelk of the ovum, while the lateral 
canals, ‘ uteri reduplicati’ of Tyson, secrete the 
albumen ; the ovum is supposed to be impreg- 
nated and incubated in the uterus, (middle cul- 
de-sac formed by the communication of the two 
vaginal canals,) out of which the young one is 
Stated to pass into the vagina (uro-genital pas- 
sage) by a particular opening, which prior to 
gestation does not exist. 
The only observations published by John 
Hunter himself relative to marsupial genera- 
tion are contained in the ‘ Zoological Appendix 
to White’s Voyage to New South Wales,’ 
where, in the introduction to his descriptions 
of the quadrupeds of that country, Mr. Hunter 
alludes to the American Opossum, and ob- 
serves, “there is something in the mode of 
propagation in this animal that deviates from 
all others ; and though known in some degree 
to be extraordinary, yet it has never been at- 
tempted, where opportunity offered, to com- 
plete the investigation. I have often endea- 
voured to breed them in England; I have 
bought a great many, and my friends have 
assisted me by bringing them or sending them 
alive, yet never could get them to breed; and 
although possessed of a great many facts re- 
specting them, I do not believe my information 
is sufficient to complete the system of propaga- 
tion in this class.” 
At this period, when it was admitted on all 
hands that some remarkable peculiarities were 
connected with the marsupial generation, and 
yet their precise nature and signification re- 
mained unelucidated by any direct and accu- 
rate observation or experiment, it is not sur- 
prising that the subject should have given rise 
to many curious hypotheses and speculations ; 
those of Sir Everard Home have already been 
noticed. I shall next briefly allude to the 
writings of M. Geoffroy St. Hilaire. 
The fruitful and discriminating labours of 
this talented Naturalist in advancing the zoolo- 
gical history of the Marsupialia cannot be too 
highly esteemed, but his attempts to elucidate 
their generative economy have been less suc- 
cessful. 
Placing an undue reliance on the relation of 
Count Aboville,t he first revived the gem- 
miparous doctrine,t meeting the objection 
afforded by Tyson’s discovery of an uterus, by 
the remark that the fetus of the marsupial 
animal has never been found there; but that 
the teats are developed in the ratio of the size 
and according to the number of the young: 
that mules equally possess a generative appa- 
ratus, which is stricken with sterility: that 
some plants with a perfect system of procrea- 
tive organs, nevertheless propagate by gemma- 
* Philos. Trans. 1819, p. 234, and Lectures on 
Comparative Anatomy, vol. iii. 
+ See the note at the end of the 2d volume of 
€ Chastelleux Voyage a l’Amerique Septentrionale, 
Paris, 1786.’ 4 
¢ Journal Complementaire du Dict. des Sciences 
Médicales, 1819. 
