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Show 392 PROF. HUXLEY ON THE REPRESENTATIVES OF [May 27, the inner side of the surface of the os articulare." (Stannius, ' d. Zootomie,' Zweiter Theil. Amphibien, p. i>8, 1856.) Prof. Peters adds to this account of the matter the following statements (Monatsberichte, 1869, pp. 593, 5 9 4 ) :- That Meckel's cartilage, which persists throughout life in the Crocodile, becomes very slender posteriorly, and passes through the hole in the os articulare; that this slender cartilage then ascends upon the posterior and upper face of the quadrate bone enclosed in a membranous sheath ; that, having reached the posterior edge of the membrana tympani, " it becomes connected with a cartilaginous plate, the narrow middle part of which is bent inwards towards tbe columella auris, with the external end of which it is connected by a joint. The broadest part of this cartilaginous plate is shaped like an axe-head, is directed perpendicularly against the membrana tympani, and forms, at the anterior end of its convex outer edge, a little plate which lies in the middle of the membrana tympani. It causes this region of the membrane to project slightly outwards, in the adult as well as in the young, and gives attachment to a filiform tendon which proceeds from the posterior boundary of the tympanic cavity. The other part of the cartilaginous plate bends away at an obtuse angle from the former, and has also the form of an axe- head, the convex edge of which, however, is narrower, and is applied below the posterior and inner part of the tympanic membrane to the cartilaginous margin of the tympanum." Prof. Peters considers that the last mentioned triangular cartilage is the homologue of the malleus. In another embryo 20^ centimetres long, Prof. Peters finds (/. c. p. 594) a "little, short, cylindrical, intermediate cartilage," which connects the columella \_stap)es~\ and this so-called malleus, and which he compares to the incus, or the os lenticulare. In a subsequent communication (7th January, 1869, Monatsberichte, pp. 6-8) " O n the cavities of the Lower Jaw in the Crocodile," Prof. Peters repeats the assertion that his so-called "malleus" is connected by a cartilaginous cord with the posterior end of Meckel's cartilage, and states that he is unable to find the duct by which (as Stannius states) the pneumatic cavity of the os articulare is placed in communication with that of the quadrate bone. Nevertheless the description given by Stannius is perfectly correct, and I am puzzled to comprehend how the pneumatic duct, which places the air-cavities of the quadrate and articular bones in communication, can be confounded with a cartilaginous rod surrounded by a membranous sheath. The fact is that there is no diiect connexion between the posterior part of Meckel's cartilage and the so-called " malleus; " and thus, I cannot but think, the whole foundation of Prof. Peters's argument collapses. Before particularly describing the very curious and instructive character of the outer extremity of the stapes (or so-called columella auris) and of the parts connected with it in the Crocodile according to m y own observations, it is proper to remark that both Cuvier and Windischmann observed, though they did not quite rightly interpret, its structure. |
