Young mice kept on a diet consisting of meat only develop an anemia which is accompanied by depressed growth and high fatality.
Treatment of mice while subsisting on the meat diet with para-aminobenzoic acid, folic acid, vitamin B12, liver extract, pyridoxine, iron, vitamin A, penicillin, aureomycin or a combination of some of these substances neither prevents the anemia nor the mortality, nor does it improve growth. Some of these substances have, however, a slight effect in preventing anemia.
Replacing one of four parts of meat by beef liver or an isocaloric-isonitrogenous mixture of casein, cornstarch, salts and water almost completely prevents the anemia but does not improve, or only slightly improves, the stunted growth. Dilution of meat with liver but not with the casein mixture has a striking therapeutic effect in mice rendered anemic by the meat diet.
It is assumed that the anemia is caused by the presence in meat of a hematopoiesis-inhibiting factor and/or by the lack of some unknown hematopoietic factor(s) possibly produced by the intestinal flora and present in liver.