16 KEPORT — 1841. 



epithelium generally, a nucleus is first [found] f formed*, and then a cell is 

 formed around it. These cells are connected by a gelatinous substance, in- 

 terspersed with minute granular bodies, which displays considerable elas- 

 ticity, and which sometimes presents a fibrous appearance. The granules 

 can be caused to disappear by compression. In certain parts of the epithelium 

 of the calf, distinct fibres are observed to pass over the surface of the scales, 

 and to connect them together, thus forming a very delicate net-work. On the 

 surface of the body and of the mucous membranes of man and animals gene- 

 rally, the superficial scales are thrown off by pressure from the cells beneath. 

 But in some cases, as with frogs and efts, the epithelium-scales are removed 

 in a continuous layer, and Mr. Nasymth is disposed to believe that it is the 

 covering which, according to naturalists, is swallowed by the animal after 

 having been shed. The cuticle and epithelium then are evidently organized 

 [tissues] f bodies*. It would appear that they are formed from a fluid 

 secretion, and that their various stages of development are as follows : 1st, 

 the formation of nuclei and their corpuscles ; 2nd, that of cells j 3rd, the 

 growth of the latter effected by vital imbibition ; 4th, their compression and 

 gradual conversion into minute lamellae or scales. The cells seem to have 

 within themselves a power of growth, and it i-emains for pathologists to deter- 

 mine what share the derangement of this function has in the production of 

 cutaneous diseases. Under certain modifications the epithelium certainly pre- 

 sents vital phsenomena, among which may be mentioned the ciliary motions. 

 Mr. Nasmyth concluded his paper by an especial description of the portion 

 of the epithelium lining the cavity of the mouth. In the foetal subject, pre- 

 vious to the extrusion of the teeth, it forms on the alveolar arch a dense pro- 

 jecting layer, distinguishable from the surrounding membrane by its whiteness, 

 and by superficial and waving ridges and sulci. The younger the subject, 

 the greater is its thickness. It is made up of a mass of scales lying one 

 above the other, and thus presents no resemblance to cartilage, though it has 

 been generally classed as such. In the interior of its structure, where it cor- 

 responds to the molar teeth, small vesicles may be frequently observed, vary- 

 ing in size from one-fourth to one-eighth of a line in diameter. On micro- 

 scopic examination, the [parietes] -|- particles* of these are found to consist 

 of attenuated scales, and their cavity to contain a fluid abounding in minute 

 granules and cells. They are probably the "glands" described by Serres as 

 intended for the secretion of the tartar. Larger vesicles are also found im- 

 planted in the vascular mucous membrane, composed of a very delicate tissue, 

 and containing a transparent fluid, which coagulates on the application of heat 

 or acid. In this fluid float numerous globules and scales, similar to those of 

 the epithelium generally. The internal or attached surface of the alveolar 

 epithelium presents numerous fringed processes, which sink into the sub- 

 stance of the subjacent mucous membrane. These ai'e found to be composed 

 of elongated scales. By immersion in water or diluted spirits of wine, these 

 fringes are much enlarged, and their size, indeed, exceeds that of the dense 

 epithelium itself. 



(B.) — Dr. Lloyd's Abstract of Mr. Nasmyth's Paper read before the Geolo- 

 gical Section at Birmingham ; printed from a copy preserved by Dr. Lloyd. ■ 



" During the author's microscopic researches on the structure of teeth, he 

 was led to the discovery of the organized nature of the interfibrous substance 

 which Purkinje, Frankel, Retzius, and Miiller have regarded as structureless, 



* The words in italics are in the Athenaeum, but are not in the original manuscript. 

 t The words in brackets are in the original manuscript, but are not in the Athenaeum. 



