Manganese, a Normal Element in the Tissues of the Fresh Water Clams, Un10 and Anodonta

Manganese in the tissues of normal animals may be regarded as a rare element. In traces it is known to be present in a number of marine animals, as was shown by Pichard.’ Hoppe-Seyler2 is authority for the statement that it is not infrequently present in human blood and in the liver: but it is neither constant in its occurrence nor significant in amount. Among the lower animals there is at least one instance on record of the normal and physiological presence of manganese in the blood and tissues. In the blood of the mollusk, Pinna sqz~~+~osa, manganese is believed to serve a respiratory function. According to the analyses made by Griffiths,3 manganese is present in the blood to the extent of 0.35 per cent. So unique was this discovery, however, that it has received little more than the passing interest given a curious fact devoid of any real physiological interest. We have to report in this preliminary notice what seems to be another normal exampleof its use in themetabolism of the fresh water clams, U&o and Anodonta, so abundant in the lakes and rivers of the Mississippi basin. While our specimens were obtained from the Madison lakes of Wisconsin only, they are thoroughly representative of the two species in every other respect, so that we are confident that specimens from other localities will exhibit this same metabolic idiosyncrasy. This point, however, will be definitely settled as soon as more material can be obtained. While the qualitative recognition of manganese in tissues containing such considerable amounts as are present in this animal