On the commissures of the cerebral hemispheres of the Marsupialia and Monotremata as compared with those of the placental mammals / by William Henry Flower.

  • Flower, William Henry, 1831-1899.
Date:
[1865]
Catalogue details

Licence: Public Domain Mark

Credit: On the commissures of the cerebral hemispheres of the Marsupialia and Monotremata as compared with those of the placental mammals / by William Henry Flower. 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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    XIII. On the Commissures of the Cerebral Hemispheres of the Marsupialia and Mono- tremata as compared with those of the Placental Mammals. By William Henry Flower, F.R.S., F.R.C.S., Conservator of the Museum of the Royal College of Surgeons of England. Received January 24,—Read February 9, 1865. The terms used in describing the anatomy of the vertebrated animals have in most cases been originally bestowed on parts of the human body, being frequently derived from some quality, relation, or real or fancied resemblance to some known object, possessed by the structure in question in Man. It will therefore be most convenient to pass from the best to the least known, and to commence by a short recapitulation of the characters and relations, in the human brain, of those parts to the consideration of which, in the brains of the lower mammalia, this communication is specially devoted. Plate XXXVI. fig. 1 is a view of the inner surface of one of the hemispheres of the human cerebrum, such parts as pass across the middle line to the other hemisphere having been divided, and those that do not belong to the hemisphere proper being removed. A convenient central point to start from in the description is the part cut through to make the section last referred to. A is the surface of the divided mass of fibres, by which the hemisphere is connected with the inferior parts of the encephalon, and with the spinal cord—the crus or peduncle of the brain. The section is made between the corpus striatum and the thalamus opticus. The thalamus, as not belonging to the hemisphere proper, and interfering with the view of essential parts, is removed. The upper and posterior portions of the circumference of the part just described are sur- rounded by the narrow slit-like opening, the “ventricular aperture” (O O), which leads into the great cavity in the interior of the hemisphere, the lateral ventricle. The inferior margin of the ventricular aperture is formed by the “taenia semicircularis,” the superior by a stronger and better marked band of white fibres, forming the free edge of the inner wall of the hemisphere, the “ fornix.” Leaving this for the present, we must next notice as an important landmark, the great or superior commissure, or “ corpus callosum” (B), here seen in its entire length, slightly arched, thick and rounded behind (the “ sple- nium” E), and curving downwards in front (the “genu” C), ending in a pointed “ros- trum ” or beak (D) directed backwards. The hinder edge is also curved upon itself, ending in a rounded edge (N) projecting downwards and forwards and folded under the main body of the corpus callosum, much in the same way, though in a less degree, as the rostrum in front. This part requires special attention in connexion with the pre- sent subject, as in the lower mammals it acquires a much greater relative importance.