Читать книгу The Book of the Pearl. The history, art, science, and industry of the queen of gems онлайн

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Examinations of many of these have failed, except in rare instances, to reveal a foreign nucleus of sand or similar inorganic substance. In searching many fresh-water mussels, Sir Everard Home frequently met with small pearls in the ovarium, and he further noticed that these, as well as oriental pearls, when split into halves, often showed a brilliant cell in the center, about equal in size to the ova of the same mollusk. From these observations, in 1826 he deduced his “abortive ova” theory, and announced:

A pearl is formed upon the external surface of an ovum, which, having been blighted, does not pass with the others into the oviduct, but remains attached to its pedicle in the ovarium, and in the following season receives a coat of nacre at the same time that the internal surface of the shell receives its annual supply. This conclusion is verified by some pearls being spherical, others having a pyramidal form, from the pedicle having received a coat of nacre as well as the ovum.^[54]

Naturalists generally accepted these conclusions, that pearls originate in pathological secretions formed, either as the result of the intrusion of hard substances, or by the encysting or covering of ova or other objects of internal origin; and there was no important cleavage of opinion until the development of the parasitic theory, as a result of the researches of the Italian naturalist Filippi, and those following his line of investigations. This theory is not severely in conflict with those of Réaumur, Linnæus, Home, etc., but relates principally to the identity of the irritating or stimulating substance which forms the nucleus of the pearl.