THE EXTERNAL EAR. 41 



or " lacunae" which intercommunicate with one another. These 

 again, by means of spaces existing between the circular fibres, 

 may stand in connection with the upper system of cavities. 

 These spaces are all lined with an endothelium, the form and 

 instability of which renders it most comparable with the epi- 

 thelium lining the layer of Descemet on the posterior surface 

 of the cornea. After treatment with solutions of silver and of 

 gold, dark- coloured looped lines forming meshes are brought 

 into view, similar to those characterising the interior of the 

 lymphatics. The relations of the framework to the remaining 

 parts of the membrana tympani, it is to be observed, are such 

 that the anterior part normally presents a similar configuration 

 to that just described, whilst it only appears as a foraminated 

 membrane in the lower parts. Yet, even here, the already- 

 described variations in the arrangement of the fibres may also 

 occur. 



Gruber, in a monograph (8), attributes a dendritic structure to a 

 fibrous framework, the position of which indeed corresponds with ours, 

 but the minuter details of which he has not sufficiently described. 



In connection with the fibrous framework, and especially in 

 children, at the marginal zone of the mucous membrane, villous 

 processes, 0'220 of a millimeter in length, and O088 of a milli- 

 meter broad, were first described by Gerlach. (These villi occur 

 also in the purse of Troeltsch and at the malleus.) They are in- 

 vested with pavement epithelium, and are composed internally 

 of connective tissue in which are seen capillary loops. 



In regard to the nerves, the bloodvessels, and the lymphatics of 

 the membrana tympani, the relations of the bloodvessels alone 

 are known through the labours of Gerlach (7), v. Troeltsch 

 (45), and Rudinger (38). In reference to the nerves, v. 

 Troeltsch states that they are chiefly or almost entirely dis- 

 tributed in the cutis, without, however, giving any further 

 account of their mode of termination; he was never able to 

 discover them in the mucous membrane ; but Gerlach (7) once 

 or twice recognized in the latter region a few fine, non- 

 medullated nerve fibres. 



The membrana propria, in accordance with the observations 

 of all who have hitherto studied its anatomy, is destitute of 



