For 2¼ years a large colony of rats was maintained on a diet based on a dietary survey of a human population. One-half of the rats was fed on the human survey diet, or this diet with a small increase in milk, the other half on the same diet supplemented with additional milk and green food. Four generations of animals were reared, all from the same stock.
The rats on the human diet with additional milk and green food were healthy in all respects so far as can be judged from our own rats on a stock diet and from the data of other workers.
On the other hand, in spite of an exactly similar environment and heredity, the animals without additional milk and green food, showed:
(1) a slightly impaired reproductive capacity;
(2) a very markedly increased death-rate due to increased susceptibility to an infection to which all rats were equally exposed;
(3) a definitely slower rate of growth;
(4) a lower haemoglobin content in the blood; and,
(5) a clinically poorer condition as judged by behaviour and state of the coat.
These findings are discussed and the possibility of applying them to human dietetic problems briefly touched upon.