On the Structure of the Brain in Marsupial Animals. [Abstract]Author(s): Richard OwenSource: Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Societyof London, Vol. 3 (1830 - 1837), p. 460Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/110538 .

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460

of an expedition which be made with a view to investigate the cir? cumstances of this remarkable meteorological phenomenon, and

proposes a theory for its explanation.

" A Meteorological Journal kept at Allenheads, 14*00 feet above the level ofthe Sea, from the 1st of May to the 1st of November, 1836." By the Rev. Wiliiam Walton. Communicated by P. M. Ro? get, M.D., Sec. R.S.

January 26, 1837.

FRANCIS BAILY, Esq., V.P. and Treasurer, in the Chair. A paper was read, " On the Structure of the Brain in Marsupial

Animals." By Richard Owen, Esq., F.R.S., Hunterian Professor o?

Anatomy to the Royal College of Surgeons. The author describes a remarkable modification in the commis-

sural apparatus, apparently provided with a view to establish com- munications between the cerebral hemispheres, which he has ob? served in the brains of marsupial animals, and which has hitherto been regarded as constituting the essential difference between the brains of oviparous and mammiferous vertebrata, but which he con? siders as indicating a certain relation between the greater perfection of that organ, resulting from the superior magnitude of the great commissure, or corpus callosum, and the placental mode of deve?

lopement in the true mammalia. In a former paper headduced evi? dence tending to show that both a small developement of the cere? bral organ, and an inferiority of intelligence are the circumstances in the habits and structure of this singular tribe of animals most con-

stantly associated with the peculiarities of their generative economy: and the repeated dissections hehas since made, an account of which is given in the present paper, have afforded him the most satisfactory confirmation of this coincidence, between a brief intra-uterine ex? istence, together with the absence ofa placental connexion between the mother and the fcetus, and an inferior degree of cerebral de? velopement. Thus, on comparing the structure ofthe brain in the Beaver and in the Wombat, he finds that the corpus callosum, or

great commissure which unites the supraventri- cular masses ofthe hemispheres in the former, as well as in all other placentally deve? loped mammalia, and which exists in addition to the fomix, or hippocampal commissure, is wholly absent in the latter animal: and that a similar deficiency exists in the brain of the Great and Bush Kangaroos, of the Vulpine Phalanger, of the Ursine and Mange's Dasyurus, and of the Virginian Opossum ; whence he infers that it is probably the characteristic feature ofthe structure ofthe marsupial division of mammalia. In this modification ofthe commissural apparatus, the Marsupiata present a structure of brain which is intermediate between that of the Placental Mammalia and Birds; and hence the Marsupiata, together with the Monotremata, may be regarded as constituting a distinct and peculiar group inthe former of these classes, although they include forms, which typify the different orders ofthe ordinary Mammalia.

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