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The study of incorrectly positioned teeth has a long history, especially in relation to human groups and domestic dogs. Dental and orthodontic specialists have been particularly concerned to establish ways of recording and comparing such anomalies. However, Colyer and others have established that anomalous dental positioning occurs in a wide variety of species, and might at times even have had adaptive advantage. In the case of dogs, some modern varieties clearly have severe malocclusion problems, while others are little affected. Because it has been suggested that early domesticated dogs already display some degree of dental crowding or malpositioning, it seems important to consider the methodology for recording such anomalies. It is suggested that a quick and easy method of recording and comparing tooth positioning is by angular measurements (preferably taken on standard photographs of occlusal views). In the British archaeological dog samples selected, it was found that tooth malpositioning (and thus malocclusion of upper and lower dentitions) was only slight, compared to the overall occurrence of such anomalies in modern dogs. It is suggested that this kind of simple procedure may be of value in the investigation of secular trends in the frequency of malpositioning and malocclusion of dogs, if not other species, through time.  相似文献   
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Different black pigments of natural origin (mineral or organic) have been examined by means of several analytical methods (colour measurements, elemental analysis and structural analysis). The results, after being compared with each other, then served as reference points in the study of the ‘Black Frieze’ of the cave of Pech Merle (Lot). After that, colour measurement was investigated in situ on the paintings as a means of displaying small differences (in hue or chroma) between the black colours. The aim of this study was to verify several hypotheses concerning the techniques used by the painters of Pech Merle, and specifically by the one(s) of the Black Frieze. A first objective was that of identifying the nature and, if possible, the origin of the black pigments used in these figures. A second objective was that of determining in which parts of the frieze one or the other (or one and the other) had been used; and the final objective was to provide new technical information that might help us better to understand how the Pech Merle frieze was produced, whether by a single painter and in one episode, for the most part, or, on the contrary, in several episodes and by a succession of different painters.  相似文献   
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