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Summary--The basic anatomy of the guinea pig ear is outlined as background for a description of two surgical approaches to the guinea pig temporal bone. These approaches provide acess to the external, middle and inner ear without significant blood loss or mortality. The superior approach, made by incision at the superior anterior attachment of the auricle and removing the lateral wall of the epitympanic space, exposes the round window, epitympanum, lateral canal, and external auditory canal, leaving the tympanic membrane intact. The inferior approach through the neck exposes the cochlea, Eustachian canal, horizontal and posterior semicircular canals, tympanic membrane, and ossicles.

A series of experiments were carried out on 55 guinea pigs in four groups to study the conditions fostering bone resorbin epidermal cysts. The first group had free grafts of canal wall skin applied to the cochlea with and without talc application. The second group had canal skin flaps applied to the cochlea with and without subsequent talc application. The third group had talc applied either to the tympanic membrane or on the cochlea. The fourth group had a canal skin flap inserted into a mucosal pocket in the bulla. The animals were killed three to four months after surgery and the temporal bones were prepared for histology. Epidermal cysts were found at the cochlea in 8 of 55 animals. Cochlear fistulas were found in 6 of 55 animals. The fistulas were associated with epidermal cysts in three cases, otitis media in two cases, and talc granuloma in one case. These experiments show that migrating skin attached to a source of epithelium is capable of inducing bone resorption. Chronic foreign body granulomas and chronic sepsis are also capable of resorbing bone. These three conditions all produce a layer of undifferentiated connective tissue containing chronic inflammatory cells lying against the resorbing bone.

Guinea pig skin col-agenase, isolated from culture medium of whole skin, was separated into two enzymatically active fractions. These two fractions have been purified extensively. Peak II fraction has been purified to homogeneity as examined by polyacrylamide gel electrophoresis. Their molecular weights are approximately 130 000 (peak I) and 40 000 (peak II). Both guinea pig skin collagenase fractions are capable of degrading the native collagen fibrils and are inhibited by serum, cysteine and EDTA. They appear to be glycoproteins. Guinea pig skin (peak II) and human skin collagenase were compared. They are both glycoproteins and have similar molecular size (Mr = 40 000). Immunodiffusion assay showed that no cross-reactivity was seen between the enzymes, indicating species specificity among collagenases.

The role of emotional factors in patients with vertigo has been widely debated. Patients with vertigo, as well as patients in two separate control groups, were tested with the Eysenck Personality Inventory (EPI), the Cornell Medical Index (CMI), and a questionarie designed to evaluate the severity of the patients symptoms in order to further investigate the role of personality and its relationship to the symptom of vertigo. In patients with Meniere disease, a strong positive correlation was found between the severity of vertigo and the EPI and CMI scores. The concept of the psychological vulnerability" is useful in explaining these findings.