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Show 1905.] THE MEMBRANOUS LABYRINTH OF CERTAIN ANIMALS. 143 March 7, 1905. Dr. W . i . Blanford, C.I.E., F.R.S., Vice-President, in the Chair. Dr. Albert A. Gray, introduced by Mr. Macleod Yearsley, F.Z.S., exhibited a series of lantern-slides made from photographs of the Membranous Labyrinth of some animals, and made the following remarks:- While the labyrinth of the fishes has been investigated by many observers and with very satisfactory results, the structure as it appears in reptiles, amphibians, birds, and mammals has not been so exhaustively treated. This is due to the difficulties of preparing the organ. These difficulties recently have been to a certain extent removed; and I propose to describe as briefly as possible some of the features which have been discovered. In Man there is found in many individuals an accessory ampulla, as I propose to term it, at the posterior end of the horizontal canal, in addition to the normal one at the anterior extremity. This ampulla does not seem to have any special physiological significance, since it is not supplied by a nerve, and moreover is not found in all individuals but only in four out of six. I have not found it in any of the lower animals except the Sturgeon, but it is quite probable that with more material at hand it will be found in some other animals. The labyrinth of the Seal is remarkable on account of its size, the irregular shape of the semicircular canals, and most of all on account of the presence of otoliths of considerable dimensions. It may be that this development of the otoliths in the Seal has some relationship to the life of the animal in the water, as it is well known that in the fish the otoliths reach a size far greater than they do in any other animal. On the other hand, it may be that the development of the otoliths, and indeed of the labyrinth as a whole, is connected in some way with the migratory habit of the Seal. The perilymphatic spaces of the semicircular canals of the Seal are, like those of Man, of considerable size, and differ in this respect from those of the Cat and the Rabbit. The Cat has a labyrinth typical in one respect of a large number of mammals; that is, in the almost complete absence of a definite perilymphatic space in the semicircular canals. Indeed, this space is not visible except at the corners where the ampullae of the canals debouch from the canals themselves. The cochlea of the Cat is part of a cone sharper than that of many mammals, but not quite so sharp as that of the Guinea-pig. The Rabbit has a labyrinth similar to that of the Cat, but the cochlea is blunter in appearance. As in the Cat, there is no perilymphatic space in the canals. The ligamentum spirale is not so well developed as in many other mammals. In addition to the already well-known features of the labyrinth P r o c . Z o o l . S o c .- 1905, V o l . I. No. X. 10 |
