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The elastic constants and ultrastructure of the basement membrane of the crystalline lens of the adult cat have been investigated. Negatively stained specimens examined by electron microscopy revealed fragments of parallel filaments showing little tendency to cross over or link with each other. High resolution micrographs also showed that the filament spacing was about 4.3 nm while the filaments had a regular periodicity of 4.1 nm along their length. Optical defraction analysis of the filaments suggested a possible helical array, the angle of tilt of the helices being about 50°. The elastic properties of the basement membrane were compared with those of a lightly vulcanized rubber membrane of the same thickness. At low stress values the Young modulus of elasticity of the basement membrane (0.82 x 10 6 Nm -2 ) and rubber membrane (1.32 x10 6 N m -2 ) were similar, but at moderate extension the basement membrane had a Young modulus of elasticity almost ten times greater than rubber which in contrast showed a slight decrease in elasticity. Also basement membrane had a low percentage of elongation (25%) compared with rubber (750 %) but the ultimate stress required to rupture basement membrane was similar to that of rubber. These data suggest that the extension of coiled superhelices of the filaments rather than the extension of non-extensile randomly linked filaments, would be an appropriate model of basement membrane. This satisfactorily predicts the stress-strain curve, and ultimate stress of the intact membrane, while on the molecular level it predicts the angle of tilt of the superhelix (53°) and indicates that the elasticity modulus of the filaments of which the membrane is composed is similar to the elasticity modulus of collagen filaments. Furthermore the change of entropy (1.0 → 1.6 J K -1 per mole of collagenous protein polypeptide residue) has been calculated from the external work necessary to rupture the membrane. In terms of the model this presumes that all the superhelices of which the membrane is composed have passed from a helical to a non-helical or extended state before rupture. A similar estimate for the growth entropy of polypeptide chains has previously been made from thermodynamic measurements on binary polypeptide solutions which induce either a random or helical configuration.

An elderly male skeleton from medieval Canterbury displayed evidence of DISH and metastatic carcinoma. The dry bone findings, SEM, and radiography suggest a primary focus in the prostate. A review of the palaeopathological literature has shown that such a finding is extremely rare in archaeological remains. This is the first reported case of prostatic carcinoma from medieval England.

Subperiosteal deposits of new bones on the visceral surfaces of ribs obtained from a variety of British Roman and Medieval cemeteries were examined by scanning electron microscopy (SEM). They showed evidence of active deposition of bone around a network of vascular grooves. A sequence of stages, from a slight deepening of the grooves to complete enclosure of the blood vessel in a bony tunnel could be recognized and, in somespecimens, several superimposed layers of new bone indicated that the process could be repeated. Microscopical evidence for osteoblastic and osteoclastic (Howships) lacunae existed in the best preserved specimens, showing the value of SEM, in demonstrating the cellular dynamics of palaeopathological processes.In the Terry Collection (Smithsonian Institution, Washington, DC) the appearance of this lesion is significantly associated with tuberculosis or other pulmonary disease. We suggest a similar correlation for British material. The importance of establishing early diagnostic criteria for respiratory infection in osteoarchaeological material is emphasized. The presence of periostitis on rib visceral surfaces is detected easily using only a hand lens and abundant material is available. It is suggested that it might form one such useful diagnostic criterion.Keywords: Palaeopathology, Scanning electron microscopy, Rib lesions, Tuberculosis.This paper is concerned with the use of microscopical techniques in the interpretation of a commonly observed skeletal lesion. Localized plaques of subperiosteal new bone deposition occur on the visceral surfaces of ribs with sufficient frequency to suggest an association with a common disease in ancient populations. The examples to be discussed are drawn from a variety of Romano-British and Early Medieval cemeteries in England. However, the same phenomenon has been observed in the dissecting room skeletal collection at Leicester and in the Terry Collection in the Department of Anthropology at the Smithsonian Institution, Washington, DC. References to similar lesions in the literature identify it in the HammannTodd Collection, Cleveland, Ohio,' in Native American ossuary materialzc3 and in Bronze Age A n a t~l i a .~ Although the lesions can be seen with a hand lens, techniques used in the present study include histology, microradiography and scanning electron microscopy (SEM) in order t o explore their structure in detail. This paper demonstrates the value of SEM in demonstrating changes, believed to be sequential, in the morphology of these lesions.Samples of ribs 1-2 cm long from affected individuals were cut free-hand with a fine hacksaw and prepared for SEM according to the method used in our preliminary study of normal ribs.' The samples were viewed from the visceral surface and in cross-section in the IS1 DS 130 scanning electron microscope, at magnifications from 8 x to 1000 x. Ribs where surface structure was obscured or destroyed by diagenetic changes were rejected for further study, and morphological features of the bone surfaces were identif...

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