The absence of the "A" type however may also manifest itself in another way, viz., by the development of an eye disease which McCollum first designated as xerophthalmia or dry eye and which the British authorities prefer to designate as keratomalacia. The failure of this result to always follow the absence of the "A" type in the diet has led some to question the specificity of this disease. While the infection of the eye is due to other agents the sum of the evidence supports McCollum and points to the absence of "A" as the true predisposing cause of the disease. Bulley, basing her claims on a study of some 500 rats fed on a synthetic diet, claims that the eye condition is not primarily due to a dietary deficiency but to an infection resulting from poor hygienic conditions.

In these groups special hygienic measures were taken against infection. Furthermore repeated attempts were made to transmit the eye disease by using sterile threads, passing them carefully over the edges of the sore lids and then carefully inoculating the eyes of other rats. These attempts resulted negatively in all cases where the inoculated rats had plenty of the "A" vitamin. Treatment of advanced cases of sore eyes with a saturated solution of boric acid and also with a silver protein solution failed to relieve the condition while as little as 2 per cent of an extract containing the "A" vitamin when added to the ration, speedily resulted in cure and increase of weight. These results combined with similar data compiled by Osborne and Mendel seem to refute Bulley's contentions and to justify our acceptance of xeropthalmia as a specific vitamin deficiency disease.

On the other hand all workers know that rats often do develop and grow well for a considerable period of time on a diet free from the "A" and without manifesting the eye disease. The British authorities explain this by assuming that animals have the power to lay down a reserve of this vitamin on which they can draw in emergency. Sherman and his coworkers confirm this power to store the vitamin. Others have been led to explain their results as due to contamination of the basal diet. Daniels and Loughlin recently maintained that the commercial lard used in basal diets and assumed to be "A" vitamin-free was supplied with sufficient of the "A" to produce growth and prevent eye disease. Their views have failed of confirmation by Osborne and Mendel. It is evident therefore that these occasional lapses from specific response to absence of the "A" vitamin need further elucidation. It is equally manifest that in the majority of cases the absence of the "A" will result in both stunted growth and xeropthalmia. The appearance of the eye disease may be taken however, as a sure indication of the absence or deficiency in the "A" vitamin.

V. Physiological Properties of the "B" Vitamin

Beri-beri is a disease that is described clinically as a form of severe peripheral neuritis and may appear in two well marked forms. In one type there is great wasting, anesthesia of the skin and finally paralysis of the limbs. In the other, the most marked symptom is excessive edema which may affect trunk, limbs and extremities. In severe cases the heart is usually involved and death may occur suddenly from heart failure.

Most observers assume that the antineuritic vitamin discovered by Funk and the water-soluble "B" are identical. This view is based on the fact that when sources which yield the water-soluble "B" in rat feeding are tested for antineuritic power these sources are apparently parallel in antineuritic power and growth production. Furthermore rats deprived of the water-soluble "B" develop polyneuroses identical in symptoms with those shown by rats and pigeons when the latter are placed on a polished rice diet.

Emmett has recently opposed this view and suggests that while the antineuritic factor and the growth factor are found in the same sources and have much in common it does not follow that they are identical and that his experiments tend to show that there are marked differences which suggest that the "B" type is not a single entity but a group. Mitchell has summarized very well the controversial phases of this question with an impartial review of the facts. One of strongest of the opposition arguments lies in the failure of milk to cure beri-beri except when administered in large quantities.

This objection has been partly allayed by data bearing on the relation of the milk content to the food of the cow. Hess, Dutcher, Hart and Steenbock and others have adduced sufficient evidence to show that the vitamin content of the milk of a cow is largely determined by the cow's food and as a consequence the milk may be very poor in vitamin. It is obvious then that the failure of the milk to cure beri-beri in a given case might be due to this cause and not to lack of identity of the curative with the growth factor. Osborne and Mendel have also shown that milk in general must not be classed among the rich sources of the vitamin, even when the cow's food is rich in vitamin. The principal facts in the controversy have been presented and at present the evidence for regarding the vitamins identical seems to be preponderant.

Recently Auguste Lumiere in Paris has put forth the view that polyneuritis is not merely a vitamin deficiency disease but a nutriment deficiency disease. He reports that he fed birds on a starvation diet, but with plenty of vitamin "B". These birds developed polyneuritis and were cured by adding to the diet plenty of polished rice. The view he wishes us to take is that all factors must be present and that the absence of the nutriment is as important as the absence of the vitamin.

In the field of nutrition the absence of the "B" type is particularly marked by the behavior of the deprived animal. Rats transferred from a vitamin-free diet to one containing the "B" only, make a much more rapid recovery toward normal (even in the absence of the "A") than do animals transferred from the vitamin-free diet to one containing the "A" and not the "B". This initial jump from addition of the "B" will not continue long in the absence of the "A", as a general rule. Hess believes that in some of his infants he was able to show markedly successful growth on the diet deficient in the "A" but rich in the "B".

Tags: Vitamins