MeCollum, Simmonds, and Parsons A21 
mucosa of the intestinal tract, and skin lesions (2). The same 
diet is shown in this paper to be deficient only with respect to 
three dietary factors, all of which can be named and but one of 
which (fat-soluble A) is of chemically unknown nature. This 
forms a strong argument against the idea that pellagra is a dis- 
ease in the same category with beri-beri, or the xerophthalmia 
which was described in the second paper of this series (9). Pel- 
7 ae ae 
Sy erae 
CHART 4, 
lagra is primarily, we believe, associated with the unsatisfactory 
character of three dietary factors as described, and there cannot 
be a specific protective substance against this syndrome as there 
is for the other diseases just enumerated. We have elsewhere 
offered chemical evidence that there is but one water-soluble in- 
dispensable food constituent of unknown chemical nature (13). 
The demonstration that neither scurvy nor pellagra belong in 
THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XXXII, NO. 3 
