MARSUPIALIA. 



319 



naiidc2 and Maffeius respecting the function of 

 the marsupial pouch; " for," says Tyson, 

 " here I find they place the mammae 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. 



The 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, in the ab- 

 sence of the usual traces of a placental organi- 

 zation ; there being in these foetuses 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 J 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 proposed 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 foetus is stated to pass imme- 

 diately from the so called corpus uteri into the 

 vagina (uro-genital passage) does not exist. 



Jn the subsequent theory of marsupial gene- 



* Buffon, Hist. Naturelle, vol. x. 



t See Nos. 3758-3777, Physiol. Catal. vol. v. 

 p. 209. 



J I adopt this term from 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. 



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 

 vag.nal 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. Geoffrey 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,f he first revived the gem- 

 miparous doctrine,j meeting the objection 

 afforded by Tyson's discovery of an uterus, by 

 the remark that the foetus 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. 



t See the note at the end of the 2d volume of 

 ' Chastelleux Voyage a 1'Amerique Septentrionale, 

 Paris, 1786.' 



$ Journal Complementaire dn Diet, des Sciences 

 Medicales, 1819. 



