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The observation of an interatticotympanic diaphragm in the middle ear (ME) cleft and the functional histology of the mucosa led to a concept of ME morphofunctional partition. There are two separate compartments: an anterioinferior one, principally devoted to the mucociliary clearance function, and a posterosuperior one, more devoted to the gas exchange function. With this concept of partition we are better able to understand the mechanisms involved in the pathogenesis of otitis media. Clinical as well as surgical management is thereby enhanced.

The morphogenesis of the tympanic part of the temporal bone The aim of this report is to describe the relative movement of the tympanic membrane and its supporting structures during embryonic and postnatal life, leading to its final position in a vertical plane. Previous studies were based on ultra thin sections which led to changes in orientation during development being missed. The importance of the present description is to provide a baseline with which abnormal ear development in certain congenital syndromes may be compared.

Basic information on the healing process of tympanic membrane perforations is scarce and sometimes contradictory. So the histological and histopathological course of the closure of tympanic membrane perforations was studied in experiments on mice and hamsters. From this investigations it seems evident that traumatic tympanic membrane perforations close nearly always spontaneously in animals. This fact must be kept in mind in the evaluation of techniques and results of tympanoplasties in animal experiments. Furthermore the squamous epithelium of the eardrum plays an important role in the regeneration of tympanic perforations. The closure of the connective tissue defect has always a tendency to lay behind the healing of the epithelial layer. This mechanism differs from the normal healing process of skin wounds where the squamous epithelium migrates over a newly formed granulation tissue layer. On the basis of these findings some practical considerations can be made on tympanoplasties in human.

Although an apparently limited subject, bone tissue in the middle ear, its structure and development, is a relatively vast one and there is no question of discussing it in detail here. On the other hand, many points still remain obscure and research workers find it sometimes difficult to understand each other clearly. We shall therefore dwell on a few points which deserve both emphasis and clarification.

This study was carried out on 100 tomograms of the petrous bone using Guillen's transorbital view of the anatomy of the middle ear. It provides basic data concerning the morphology, size and surface area of the tympanum, the epitympanum and the hypotympanum. It correlates the surface area of the epi- and hypotympanum, and suggests certain embryological interpretation. This study contributes to the diagnostic radiology of the middle ear in the following ways: 1 It provides basic data for the interpretation of tomograms in patients with ossicular dislocation. 2 It provides essential data for the radiology of congenital malformation and of tumours. 3 It puts in perspective certain criteria used for the diagnosis of cholesteatoma. Finally, this study justifies the use of preoperative radiological investigation.