[Activity of serum sodium, potassium and calcium in vertebrates].

In all the animals studied (the lamprey Lampetra fluviatilis, teleosts Onchorhynchus nerka, O. kisutch, Limanda aspera, Salvelinus malma, frog Rana ridibunda, tortoise Agryonemys horsfieldi, hen, albino rat) and man, sodium and potassium were found in the blood serum in a free form, both before and after the addition of their salts in vitro. The initial level of active Ca varies within 20--42% of its total content in the serum. Significant interspecific differences were found with respect to the degree of Ca binding by albumin.