On the relation between the structure, function, distribution and origin of the cranial nerves : together with a theory of the origin of the nervous system of Vertebrata / by W.H. Gaskell.

  • Gaskell, Walter Holbrook, 1847-1914.
Date:
[1890]
Catalogue details

Licence: Public Domain Mark

Credit: On the relation between the structure, function, distribution and origin of the cranial nerves : together with a theory of the origin of the nervous system of Vertebrata / by W.H. Gaskell. 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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    together of its walls; tlie appearance of a tube lying flat is much enhanced by the presence of a row of blood vessels between it and the brain proper. In Fig. 3, PI. XX, I represent a series of sections through this canal at different distances from the infundibulum. The examination of other cases is very instructive. Thus in the skate the series of sections through this region shows how the terminal portion of this tube has been fixed down and partially obliterated while the next portion has been distended and folded to form the saccus vasculosus. I have also found the same appearance in the brain of the dog-fish; the diagram on PI. XVIII is drawn from one of the series of longitudinal sections through the brain of a young dog-fish and is a fairly accurate representation of the shape of the brain cavity; the dorsal masses of nervous matter are not drawn to scale but simply indicated so as to show roughly the relation of parts. In that figure the position of this folded down tube is clearly shown. In Fig. 1, PI. XX, I give a sketch of the ventral surface of the brain of a dog-fish to show the position of this folded down tube and the position in which the brain was hardened for the purpose of making a series of sections through this tube. The pituitary body, the saccus vasculosus and the lobi infundibuli were all turned back on to the optic chiasma as far as possible ; the brain was then placed in picric acid, hardened, stained, and a series of sections cut through the part indicated by the lines drawn across Fig. 1. Fig. 2, PI. XX, represents a selection out of the whole series of transverse sections through this part of the brain. They disclose clearly the fact that the cavity of the infundibulum not only forms the cavity of the lobi infundibuli and of the saccus vasculosus but is continued on the surface of the brain backwards beyond the limits of the saccus vasculosus as a tube which becomes more and more superficial. An examination of the separate sections shows that this tube forms a distinct projection on the surface of the brain and at first it possesses a conspicuous lumen lined with epithelial cells of the same character as those lining the rest of the central canal. In the 3rd section represented the last remains of the cells lining the lumen is seen, but as is seen in the 4;th, 5th and 6th sections the walls of the tube not only continue to appear in each section but come to lie more and more outside the nervous matter, so that in the last two sections the continuation of the walls of this tube is seen as a small mass of peculiarly structureless tissue entirely surrounded by pia mater and blood vessels and so lying freely on the surface of the