450 Messrs. W. Cramer, A. H. Drew, and J. C. Mottram. 



rats develop infective conditions, which attack most frequently the eyes, and 

 xerophthalmia develops. There may be other organs affected (septic glands or 

 pneumonia sometimes develop). 



These infective conditions develop most rapidly in those rats which show 

 the " acute " effect on growth, when it may first appear after 6-8 weeks. 

 In the rats showing only the " chronic " effect on growth, an infection may 

 not develop at all or very much later. We have kept rats on a fat-soluble 

 vitamin-free diet for four months without any infection appearing, although 

 these rats were kept in the same cage with rats which had developed a very 

 intense xerophthalmia. The external appearance of these rats was, in fact, 

 such as to make them indistinguishable from normal rats. It will be shown, 

 however, that such rats develop the lesion which we consider to be specific 

 for the vitamin A deficiency, although not to the same extent as rats 

 exhibiting the acute effect on growth. The condition of nutrition of rats on 

 a vitamin A-free diet varies, as is to be expected. The rats which show the 

 acute condition are ill-nourished, but the extreme condition of emaciation 

 seen in the rats suffering from the B deficiency is hardly ever met with. 

 Another important difference is that the progressive fall of temperature, 

 which is so characteristic of the B deficiency, does not appear in the 

 A deficiency. 



We have been able to control experimentally the conditions under which 

 the " acute " and "chronic" effects of fat-soluble vitamin deficiency appear. 

 Hitherto, the reason for these differences has not been understood. One 

 important factor is the nature of the diet which the rats have received in 

 infancy. If the mother during pregnancy and lactation has received a diet 

 rich in vitamins, and if this diet be given to the young rats after they have 

 been weaned, then the rats are found to be more resistant to a subsequent 

 withdrawal of the fat-soluble vitamin. If, on the other hand, the diet has 

 not been particularly rich in vitamins, although it may contain an amount 

 adequate to maintain the animals in health and to enable them to grow and 

 to breed freely, then withdrawal of the fat-soluble vitamin will produce an 

 immediate and " acute " effect. It may be added that the diet we refer to 

 is not an artificial one, but a natural diet of bread and water, rice and 

 maize, which has for years been used in our laboratory as the standard diet 

 for our stock of rats. Incidentally, this clearly emphasises the great 

 importance of assuring an ample supply of vitamins to the pregnant and 

 lactating woman, and to children, and of not being satisfied with the 

 comfortable belief that our ordinary food contains sufficient vitamins, 

 because we do not suffer from deficiency diseases. 



Another factor which determines the onset of xerophthalmia is the amount 



