[Unexpected demonstration of copper deficiency in the rat]

During many years, Wistar's rats were fed after weaning a semipurified diet containing 0.4 ppm copper and did not present clinical disorders of copper deficiency. Rats of same strain fed on the same diet, but housed in a new physical environment presented, a year later, specific signs of deficiency. A new salt-mixture raising the copper content of the diet to, 5.2 ppm made the deficiency signs diseapear and the rats growth come back to the initial rate. These results showed once again the important relations existing between the organism and its physical environment, the diet being just one of these elements. Rigorous breeding conditions, animal selection and modernisation of animal houses involve a specific feeding related to this new conditions particularly when semipurified diets are used for weaning rats.