Volume 1

[Report of the Council respecting the publication of A. Nasmyth's papers on the structure of the teeth].

  • British Association for the Advancement of Science. Meeting
Date:
[1841]
Catalogue details

Licence: Public Domain Mark

Credit: [Report of the Council respecting the publication of A. Nasmyth's papers on the structure of the teeth]. Source: Wellcome Collection.

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    and which he is disposed to believe is so characteristic in different animals as to be capable of affording valuable aid in the classification of the animal kingdom. This structure he first observed in a section of a fossil tooth of a rhinoceros, by the aid of a magnifying power of one-tenth of an inch focal distance, with an achromatic condenser of the light. The section presented an appearance of cells or compartments, the form of the cells varying in different animals; the structure also of the fibres of different teeth present¬ ing an interrupted or baccated appearance; the size and relative position of these divisions of a fibre differing in various series of animals. In man, each division is of an oval form, and connected [by] their longer axes, which correspond with the course of the fibre. In some species of quadrumana, the fibre appears to consist of two parallel rows of compartments. In the orang outang, the form is rhomboidal; and in the baboon, they are oval, as in man. The laminated concentric structure of the tusk of the mammoth, the strength of ivory when cut parallel to the long axis of the tusk, and its weakness if cut at right angles, are urged in corroboration of this peculiar structure. The structure of the enamel, as seen in a section parallel to the long axis of a tooth, presents compartments of a semicircular form ; the con¬ vexity of the semicircle looks upwards towards the free external portion of the tooth. The chemical composition of the enamel has hitherto led to the conclusion of there being only a small portion of animal matter in enamel. From Dr. Thomson’s recent analysis it appears that this has been much • understated. The pulp is observed to be cellular throughout its internal structure, and this structure is essentially concerned in the development of the ivory, in the production [of] both [the] fibres as well as of the inter- fibrous substance. There exists a great analogy between the internal or pro¬ ductive surface of the capsule and the external or productive surface of the pulp. The membranous investment of the enamel in human teeth, lately discovered by the author, displays a similar arrangement. The crusta petrosa is provided with a membranous investment. “ The above is a correct copy of my rough copy. (Signed) “ G. Lloyd*.” (C.)—Mr. Nasmyth's Abstract of the Three Payers, sent to Mr. Phillips on the %A>th February 1840, abbreviated at Mr. Phillips's suggestion, and finally corrected by Mr. Nasmyth in its progress through the Press in May 1840. The italics are Mr. Nasmyth's. 1. The Capsular Investment of the Enamel.—-The Crusta Petrosa, said Mr. Nasmyth, had been described after Retzius, Purkinje and Frankel, as a layer external to the ivory of the fangs of the simple and compound teeth of man, and mammalia generally, but as not present in the simple teeth, as a covering to the enamel. Now this latter position he not only controverted, but maintained, in direct opposition to it, that the enamel itself possesses in all instances a distinct envelope or coating. On the incisors and other simple teeth of many animals he had succeeded in tracing, in this envelope, the corpuscles of Purkinje, analogous to those found in bonef. 2. Mr. Nasmyth next passed to the consideration of the interjibrous sub¬ stance of the ivory. Purkinje and Frankel had stated that “ the proper den- * The words within brackets are noticed by Dr. Lloyd as having been accidentally omitted in his original manuscript, and were since supplied by him as being necessary for the sense. f In the 8th Vol. of the Med. and Chir. Transactions is a paper by Mr. Nasmyth contain¬ ing a full account of his discovery of the Capsular Investment of the Enamel. C