The bile coming at one time from different portions of the liver of the dog has nearly the same amount of pigment per cubic centimeter. With this determined we have studied the power of the gall bladder to concentrate bile directed to it, using as criterion the pigment strength of a sample collected throughout the period of experiment from a duct branch. The extent and rapidity of the concentration are alike remarkable. A gall bladder emptied at the beginning of one experiment and left to fill from the liver, concentrated the 49.8 cc. of bile reaching it in 22½ hours to 4.6 cc., that is to say reduced its bulk 10.8 times; while another bladder left distended with a bile of known constitution and receiving in addition fresh increments from the liver concentrated the secretion 8.9 times in 22 hours. A series of five emptied bladders concentrated the bile coming to them in about 24 hours on the average 7.1 times, or a little more than the 6.4 times of seven organs left full. The conditions in both cases were relatively unfavorable to the withdrawal of fluid from the bile because this takes place by osmosis and diffusion, with the ultimate Δ always that of the blood, and the secretion in our animals was notably rich in solids as an indirect result of the operation.

The rapidity with which fluid is withdrawn through the wall of the bladder may be judged from some experiments in which a bag was connected with the tip of the organ by a large cannula. Merely in its passage through the bladder the bile was concentrated 2.3 to 4.8 times. The finding indicates a potential source of error in observations upon samples of bile obtained from fistulous channels of which the bladder forms a part.

The bile ducts do not withdraw fluid from the secretion they convey but tend to dilute it, as we shall show in a companion paper. The restriction of the concentrating activity to the receptaculum chyli is good evidence that the latter has special significance for the organism. The nature of this significance is briefly discussed.

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