That experimental animals which have been deprived of vitamin A are highly susceptible to respiratory infections has been demonstrated by scores of research workers. The lack of this vitamin in the dietary of man has also been observed to result in similar types of infections, including the common cold.1
The recent studies of Green, Pindar, Davis and Mellanby2 indicated that concentrates of vitamin A have a therapeutic value in the treatment of certain infections, for example, puerperal sepsis. Their reports as to the value of the vitamin as a prophylactic agent against infections are also convincing. McCarrison attributed the comparative freedom from respiratory infections among certain Indian tribes to the adequacy of their dietary in vitamin A. In marked contrast to these Indians, the tribes whose diets showed a definite lack of vitamin A generally suffered from respiratory infections.
Recent experimental work has shown the relation between vitamin