By repeated weekly intravenous injections of gum acacia solution in dogs over periods of 4 to 5 months, it has been possible to maintain plasma protein concentration and total circulating protein at very low levels.

If sufficient numbers of such injections are given and then discontinued, plasma protein concentration will remain below the normal limits for several more months. Acacia remains in the blood during this time.

Reduction of fibrinogen concentration in such animals is out of proportion to and more marked than the changes in plasma protein concentration. This would indicate interference with liver function.

Plasma volume when determined at 7 day intervals during injection periods at first diminishes, then rises 20 to 25 per cent above basal levels. The total blood volume does not show such marked changes because of a decrease in red cell volume.

Globulins are reduced to a greater extent than albumin after a single injection of gum acacia, although both albumin and the globulins diminish. This cannot be accounted for by a decrease in fibrinogen alone. After 14 to 16 weekly injections, both albumin and globulins are more profoundly reduced.

During injection periods in such animals, it has not been possible to control quantitatively the dietary intake, a complication which has made it difficult to ascertain the effect of various protein diets upon the protein-acacia balance. The changes described, however, have taken place regardless of various types of animal protein diets.

Following periods of injection, in spite of very low plasma protein concentration and high acacia concentration in the blood, most of the dogs eat well and therefore they can be used during this period for controlled dietary experiments which may be of value in investigating the mechanism of the production and function of the plasma proteins.

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