The effect of ultra-violet rays on rats,deprived of vitamine A in their diet

Experiments have demonstrated that both xerophthalmia and rickets can be prevented and cured by the administration of cod liver oil, and that rickets can be cured and prevented by sunlight and ultra-violet light.

We know that the absence of vitamine A from the diet will produce xerophthalmia, and it was believed by some workers, notably Mellanby, that the same deficiency is responsible for rickets. It is generally agreed, however, that the two above named pathological conditions are distinct entities and our experiments bear out this opinion. We have investigated whether light has any noticeable effect on growth and xerophthalmia in analogy to its effect on rickets, presumably on account of a better utilization of the stored vitamine A in the body.

With this view in mind the following experiment was undertaken:

Twelve young rats of the same age were placed upon a diet as nearly free as possible from vitamine A. The diet used was that of Osborne and Mendel (with oxidised casein and oxidised lard), and as source of B vitamine, a yeast preparation was added. The rats were divided into two lots of six each. One lot was exposed for five minutes daily to the action of a carbon arc lamp for three weeks, and for the remainder of the experiment for three minutes daily, except Sunday, to ultra violet light. The animals were kept in an animal room that received the usual amount of daylight.

It can be seen from the table that there was no difference as regard the rate of growth and incidence of xerophthalmia as the result of treatment with ultra viollet light. We could not tell whether the earlier development of xerophthalmia in the males is of any significance or only purely accidental.