On the structure of the brain in marsupial animals / by Richard Owen.

  • Owen, Richard, Sir, 1804-1892.
Date:
1837
Catalogue details

Licence: Public Domain Mark

Credit: On the structure of the brain in marsupial animals / by Richard Owen. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    VIII. On the Structure of the Brain in Marsupial Animals. By Richard Owen, Esq. F.R.S. Hunterian Professor of Anatomy to the Royal College of Surgeons. Received October 31, 1836,—Read January 26, 1837. The brain in Mammalia is essentially characterized by the complexity and mag- nitude of the apparatus by which its different masses are brought into communica- tion with one another. With respect to size, the cerebral hemispheres are in many species proportionally inferior to those of Birds; and in most Insectivorous and Ro- dent Mammalia they present an equally smooth and uniform external surface; but notwithstanding the absence of convolutions and diminished size of the cerebral he- mispheres in such Mammalia, a large apparatus of medullary fibres is present, which connect together either the opposite hemispheres, or the distant parts of the same hemisphere; and this apparatus, or great commissure, is superadded to the anterior, posterior, and soft commissures, which, with the exception of a very slight rudiment of the fornix, are alone developed in birds for the purpose of uniting the opposite hemispheres. In the higher Mammalia, in which the cerebral hemispheres acquire superior size and increased extent of surface by means of convolutions, the super- added commissural apparatus presents a corresponding development and a highly complicated structure; its several parts being distinguished as the corpus callosum, fornix, and their intercommunicating laminee, termed the septum lucidum. The fornix, by means of its posterior crura and the intermediate medullary tract termed the lyra, brings the hippocampi majores into communication with each other, and with the posterior folds of the corpus callosum*; by means of its anterior crura it establishes a communication between the hippocampi and the optic thalami; and by means of the septum lucidum its connexion with the corpus callosum is continued to the anterior fold of that body-f-. In the Human brain the fornix, though of complex structure and developed as a very distinct part, is of small size as compared with the corpus callosum ; while the delicate * “ The fasciculi from tbe fornix form in part the covering of the hippocampus, and in part its loose fold, the taenia hippocampi.”—Reil in Mayo’s Anatomical Commentaries, p. 116. “ L’envelope medullaire de la come d’Ammon se continue avec la partie posterieure du corps calleux, et en partie aussi avec le pilier posterieur de la voute: c’est dans ce dernier que va se jeter le corps frange tout entier.”—Meckfl, Anatomie Descript, tom. ii. p. 679. t “ Ainsi la voute represente une chaine tres complexe qui unit les deux hemispheres l’un avec l’autre sur plusieurs points, et qui, de plus, etablit une communication entre la partie anterieure et la partie posterieure de chaque hemisphere.”—Meckel, Anatomie Descript, tom. ii. p. 658.