Various Vitamines.—The anti-neuritis vitamine is soluble in water and alcohol and is comparatively thermostable (destroyed by a temperature of 120°C. in two hours). It is affected by alkaline reaction but is stable in acid solution. The water soluble B vitamine does not seem to be destroyed by a temperature of 120°C. for two hours, hence it may be different from the anti-neuritis one. The antiscorbutic vitamines differ in being thermolabile, these factors in certain foods being destroyed by a temperature of 60°C. Another vitamine, fat soluble A, found particularly in butter, seed embryos and leaves of plants, is a food essential. Its absence from a diet causes xerophthalmia. Cod-liver oil and glandular organs of animals contain it.
Schaumann considers malt as richer in the anti-neuritis vitamine than any other article of diet, rice bran coming next. Many think that vitamines have not as yet been separated but that they are intimately combined with some mother substance in the food.
There is, in all probability, a large number of vitamines present in various animal and vegetable foods, the deficiency of which in a diet may lead to vague disorders or to well-recognized diseases, such as scurvy, ship beriberi, beriberi or pellagra.
Schaumann considers the curative principle to be of the nature of an activator. An increase in the ingestion of carbohydrates and necessarily in the vitamine as well seems to produce neuritis more rapidly than where a smaller amount is given, this indicating the importance of these vitamines in carbohydrate metabolism.
There are those who deny this carbohydrate metabolism function of vitamines and it is a fact that polyneuritis of fowls will develop on a diet from which carbohydrates are excluded.
In epidemics of beriberi it has been observed that those who eat most rice are more often attacked, thus men more frequently than women. A temperature of 120°C. destroys the vitamine. Owing to the absence of rice as a constituent of other than slightest importance in the dietary of Brazilian cases of beriberi, as well as from numerous reports of the occurrence of the disease in nonrice-eating persons, the view that is now entertained is that not only polished rice, but any predominating carbohydrate article of diet, which is deficient in the neuritis-preventing substance, can produce beriberi. Wellman and Bass have shown that such articles of diet as sago, boiled white potatoes, corn grits and macaroni practically parallel polished rice in the production of polyneuritis in fowls.
Predisposing Causes.—There does not seem to be any racial predisposition other than that associated with the more varied and the more neuritis-preventing diet of the white race. For the same reason beriberi is more prevalent among the poor than among the prosperous classes of countries where the disease exists extensively.
It is customary to consider as predisposing causes bad hygienic surroundings, such as occur in jails, camps, etc., as well as the influence of warmth and dampness of the atmosphere. Beriberi is more common among men than women and affects most commonly individuals between 15 and 30 years of age. Physical exhaustion, excessive grief, digestive derangements, abuse of alcohol and tobacco are considered to have a bearing in the production of the beriberi symptoms. Surgical operations may be followed by manifestations of the disease.
Epidemiology.—Inasmuch as the experiments of Strong force us to the conclusion that the disease is not infectious, the study of the prevention of the disease would appear to rest almost exclusively in the question of a neuritis-preventing dietary.
In this connection Heiser, in the Philippines, has reported that with a diet in which polished rice was contained the monthly death rate at the leper colony at Culion was approximately 100, the majority of these deaths being from beriberi. As a result of the substitution of unpolished rice, about 1909, the monthly death rate fell to less than 20 and of these none were from beriberi.