Detailed abstracts of papers on 1.- The morphological relations of the nervous systems in the annulose and vertebrate types of organization. 2.- The morphological constitution of the skeleton of the vertebrate head. 3.- The morphological constitution of limbs : communicated to the Cheltenham meeting of the British Association, August 1856 / by Professor Goodsir.

Goodsir, John, 1814-1867.

Date:: [1857]

Credit: Detailed abstracts of papers on 1.- The morphological relations of the nervous systems in the annulose and vertebrate types of organization. 2.- The morphological constitution of the skeleton of the vertebrate head. 3.- The morphological constitution of limbs : communicated to the Cheltenham meeting of the British Association, August 1856 / by Professor Goodsir. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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head of the malleus. As the Eustachian tube, the tympanum, and the ex- ternal auditory passage, consist of the persistent upper portion of the first visceral cleft, the cartilage of the Eustachian tube, and the tympanic bone, ■which are continuous with one another, and tbrm the floor of these three spaces, are developed in blastema deposited near the upper extremity of the clefl. This blastema also forms the membrane of the tympanum, into which the handle of the malleus shoots. It is to be observed that this lower jaw and tympanic bone do not originate in the primordial cartilagi- nous streak, but in blastema deposited around it. The tympanic bone forms at first an inverted arch across the visceral cleft, or a ring incom- plete above, which supports the membrane of the tympanum on the outer side of the attenuated portion of Meckel's cartilage, which connects the malleus to the inner side of the jaw. It then extends inwards, so as to form the floor of the tympanum and Eustachian tube, folding up before and behind, and thus inclosing the incus and malleus leaves, the latter connected to the jaw through the tympanic fissure. The development of the first post-stomal visceral lamina appears, there- fore, to indicate at least four elements on each side of the mandibular hgemal arch in the Mammal. The tympanic element is probably com- plex ; the mandibular consists of at least two portions, one on the outer, the other on the inner side of the corresponding portion of Meckel's cartilage. In the Bird the omoid and palate bones arc lormed like the pterygoid and palate bones of the Mammal, in the so-called superior maxillary process. In the proper first post-stomal visceral lamina, the primordial cartilaginous streak divides, as in the Mammal, into two portions. The upper and smaller of the two becomes the quadrate bone ; the lower and longer portion—Meckel's cartilage—becomes enveloped in the correspond- ing half of the lower jaw ; but instead of the upper end of this portion forming the slender process of a malleus, it remains as the peculiarly- formed articular piece of the jaw itself. The original intimate connection of the rudiment of the pterygoid bone, in the so-called superior maxil- lary process, with the upper or incudal portion of the primordial carti- laginous streak of the first post-stomal visceral lamina of the Mammal, speedily diminishes; but in the Bird, not only does the pterygoid or omoid bone rapidly increase in relative size and configuration ; but the quadrate portion of the first visceral streak does so likewise. The latter also exhibits, attached to its outer side, as the omoid is to its internal pro- cess, a styliform ossicle, the rudiment of the quadrate-jugal bone, which again is connected anteriorly to the jugal. Reichart, who has minutely described and figured the development of this visceral lamina in the Bird, makes no allusion to the remarkable in- dication which it affords of the signification of the quadrate bone, and articular piece of the lower jaw. It affords, as it appears to me, sufficient evidence that the quadrate bone of the Bird is the homologue of the Mam- malian incus, and that the articular piece of its lower jaw is the homo- logue of that ossified portion of the upper end of Meckel's cartilage, which in the Mammal forms the slender process of the malleus. The quadrate bone has been hitherto considered as the homologue of the tympanic bone in the Mammal, not only from the proximity of the latter to the condyle of the jaw, but chiefly from its presumed absence in the skull of the Bird. But there appears to me to be sufficient evidence of its existence, not only in the fibro-cartilaginous frame which connects the margin of the tympanic membrane to the mastoid, lateral occipital, and basi-sphenoid,but more particularly in the thin well-defined lamina of bone, which, apparently united to its fellow of the opposite side, forms the floor of the tympanic cellular space in the broad posterior portion of the basi-sphenoid. As these apparently united laminaj are continuous with the

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