The Inorganic Constitution of Molluscan Blood and Muscle

Estimations of sodium, potassium, calcium, magnesium, chloride and sulphate have been made on the blood and muscle of marine molluscs and of the freshwater clam, Anodonta . On comparing marine blood with sea water it appears that the cephalopods show a regulatory power (i.e. difference between blood and sea water) with respect to all ions tested except sulphate. The gastropods have a regulatory power for calcium, magnesium and chloride; the pelecypods for calcium and magnesium. Calcium is always higher in blood than in sea water, while magnesium is lower. Chloride, where it differs, is lower. If muscle is considered as two phases, cells and intercellular blood space, then from whole muscle and blood analyses it is possible to calculate the spaces between the cells, which work out at 11 % for pelecypods and 18 % for the other two groups. Further calculation gives the constitution of the cells themselves, leading to the conclusion that, of the ions under consideration, only K is present in the Pelecypoda and Cephalopoda, while the Gastropoda may have some Ca and Mg as well as K. As expected the fresh-water clam contains little inorganic material. In relative proportions its blood is characterized by more calcium and less magnesium and chloride than that of marine forms. In muscle cells potassium dominates but other ions are present as well. This work was carried out at the Laboratory of the Marine Biological Association, Plymouth, in the summers of 1936 and 1937, and at the Oceanographic Institution, Woods Hole, in 1939. It is a pleasure to express our thanks to the Directors and Staffs of these establishments for accommodation,facilities and advice during the progress of the investigation.