McCollum, Simmonds, and Parsons 413 
It is obviously of the greatest importance that we have a 
correct understanding of the relation of diet to disease, and it is 
accordingly exceedingly desirable that it be definitely established 
whether there is in reality but a single essential substance in each 
of what we term fat-soluble A and water-soluble B. If, as the 
evidence available indicates, each represents but a single sub- 
stance, there can be but two deficiency diseases in the sense in 
which Funk employed this term (8). He used the term “de- 
ficiency diseases”’ to designate a series of four or more syndromes, 
beri-beri, scurvy, pellagra, and rickets, and expressed the belief 
that each was due to the lack of a specific protective substance. 
We have, therefore, directed our efforts to the solution of the 
problem concerning the number of the unidentified dietary es- 
sentials, and have repeatedly expressed the view that there are 
but two (9). 
McCollum and Pitz (10) demonstrated that scurvy in the guinea pig 
does not belong in the category of ‘‘deficiency’’ diseases, and referred it 
instead to the agency of microorganisms in the digestive tract. The stag- 
nation of feces in the cecum of the guinea pigs employed as experimental 
animals was suggested to be the primary cause of the development of the 
organisms concerned. Hess (11) has recently described experiments which 
support our conclusions regarding the bacteriological factor in the pro- 
duction of scurvy. He found that freshly pasteurized milk does not pro- 
duce scurvy in the human infant, whereas the same milk kept 24 hours 
after the heat treatment may do so. The most plausible explanation for 
this is the development of pernicious forms of organisms after the pas- 
teurization has checked the lactic acid formers. We hold, therefore, that 
scurvy has been definitely eliminated from the list of supposed ‘‘deficiency”’ 
diseases. 
In the previous articles of this series, we have analyzed the 
deficiencies of several seeds, from the dietary standpoint, by suit- 
ably planned feeding experiments (12, 13). We have arrived at 
the conclusion that beri-beri was properly judged by Funk as 
to the cause of its origin, but that the other diseases which he 
held to be due to the lack of specific substances from the diet are 
in reality due to other causes. We have called attention to clini- 
eal evidence of the existence in man of cases of xerophthalmia 
(9), entirely analogous in origin to the same pathological state in 
rats, brought about by a deficiency of the fat-soluble A in the 
diet. Xerophthalmia and polyneuritis are abundantly demon- 
