O N E FIGURE
It has been repeatedly shown by Hober and his associates that the isolated liver of the frog is able to perform secretion, in the form of osmotic work, by concentrating dilute dye presented to it in the perfusion fluid. (IIober and Titajew, '29 ; . Haywood and Hober, '37 ; Hober, '39). Dye concentrations in the bile of several hundred times have been commonly obtained, and even 1000-f old concentrations have occurred. The variety of dyes actively transferred in this way is a wide one. Limitation to their secretion is apparently a matter of colloidal size, which physically keeps out the dye, or of lipoid solubility, which causes the dye to be held by the fatty materials of the liver, or of the absence of the appropriate balance of hydrophilic and hydrophobic groups in the molecule for promoting secretion (Hober, '40).
I n the work here presented we have found that the isolated livers of fishes a r e capable of a similar secretory power toward dyestuffs. At the same time, we have obtained incidental information which has a possible bearing upon dye concentration as a secretory process.
MATERIAL
The greater number of experiments were done on the rainbow trout, Salmo irideus, and on the brown trout, Salmo f a r i ~. ~ ' A number of experiments were ahno attempted with the brook trout, Salvelinus fontenalin, but without aucwss. For anatomical remona, the carp, Cyprinus carpio, and the common pickerel, Esox reticulatun, were also found nnauitable 85 material.
*We
are indebted t o Mr. J. Arthur Kitson of the Department of Conamation of Massachusetts for permiadon to obtain a number of trout from the Htate Fish Hatcheries a t Hunder-, land and at Montague, Mass. Other trout were purchaaed from the Willow Brook Trout Hatchery at Southwick, Mass. Trout from the latter source had a much Inter breeding season than did those from the Htste Firrh Hatcheries.