On the Assaying of the Potency of Liver Extract.

Abstract

In a previous paper 1 a method was described for determining in a qualitative fashion the efficacy of liver extracts. It consisted essentially in feeding varying quantities of the extract to fowls suffering from a naturally occurring disease, which resembles very closely pernicious anemia of human beings.

The procedure has since been elaborated so as to put it more or less on a quantitative footing. Liver extract does not seem to be well absorbed from the alimentary tract of fowls, and resort has been made to intraperitoneal injection with the result that there has been a very considerable lowering of the dose necessary to produce a “response” or indicator for purposes of standardization.

The procedure for standardization consists of the injection intraperitoneally twice daily over a period of time of increasing small doses of the extract until a dose is reached at which a “response” is obtained. This “response” consists in a definite rise in the hemoglobin and red blood cell curves, appearing sharply and for the first time.

The “response” for the same extract sample appears to be obtained at the same dosage, whatever may be the state of the marrow, as regards hyperplasia, etc., provided the marrow is in a condition of hyperplasia and has not become aplastic.

The “response” dose for fowls of the White Leghorn breed of about 1500 gm. weight and kept under fairly ordinary laboratory conditions is in the neighborhood of 0.225 gm. per day of the extracts employed. These were different samples of Extract No. 343, prepared by Eli Lilly & Co., Indianapolis.

At times there is difficulty in procuring experimental fowls. It is practically certain that the majority of cases of pernicious anemia in the fowl are due to infestation with the tape worm, Davainea proglottina.