Vedder (20) has brought together a number of salient facts derived from the observations of several students of pellagra, and interprets them as showing that "there is a certain similarity between pellagra and other known deficiency diseases, namely, beri-beri and scurvy," and "much of the evidence that has been presented as a proof of the infectious nature of pellagra can be reasonably explained in accordance with a deficiency hypothesis." He further concludes: "A deficiency is demonstrable in the diets of most pellagrins. This deficiency appears to me to result from the too exclusive use of wheat flour, in association with corn-meal, salt meats and canned goods, foods that are known to be deficient in vitamins."

Vedder has brought out some very important points. "The gastro-intestinal lesions in pellagra and scurvy are analogous." Diarrhea, enteritis, ulceration of the intestines and hemorrhage into the mucous membranes are observed in both conditions. "There are similar nervous symptoms in pellagra and scurvy." Osier (21) states that scurvy is to be differentiated from pellagra.

Suggestive similarities exist between pellagra and beri-beri. The mucous membranes of the stomach and duodenum may be swollen and inflamed, and may present ecchymoses and erosions. "Similarities in the lesions in the nervous system and in the symptomatology referable to the nervous system in pellagra and beri-beri can be distinguished. The pathologic alterations that occur in the cord in pellagra are profound and striking." It has been repeatedly demonstrated that in beri-beri there is degeneration of many of the motor cells in the cord. Roberts (22) describes the extensive degenerations which have been observed in the spinal cord in pellagra. Vedder states "Now, if we compare this picture (20) with the changes found in the cord in beri-beri, we find that beri-beri is characterized by the same scattered degeneration of the fibers and similar changes in the cells of the cord."

Vedder points out that central neuritic symptoms are very common in pellagrins, and that exactly such changes in the nervous system caused beri-beri for many years to be regarded as an intoxication. "The fact that the spinal fluid in pellagra is normal, points toward deficiency, since it seems improbable that such extensive changes in the spinal cord could occur as the result of an infection without producing the corresponding changes in the spinal fluid. Even the skin lesions which are so characteristic of pellagra may be referable to changes in the cord. Otherwise, how can we explain the marvellous symmetry that is practically the constant characteristic of this symptom?" These are certainly very pertinent questions to raise in connection with any decision as to the nature of the factors involved in the etiology of pellagra.

It is evident from the discussion presented above of the conflicting evidence which is presented in the extensive literature relating to pellagra, that it is not at present possible to give credence to all the data which appear to emanate from reliable sources, and to be derived from observations which seem to be accurate, and formulate any satisfactory theory concerning its etiology. Epidemiological, clinical and chemical methods have alike failed to establish beyond question the cause of the disease.