VITAMINS 279 



discovery he believed that this was the key to the differ- 

 ence between his diets and those of Osborne and Mendel 

 and he christened this new substance "unidentified 

 dietary factor fat-soluble A." 



But there was another factor in the mixtures en- 

 tirely unsuspected by either McCollum or Osborne and 

 Mendel at the time. This factor was present in the 

 protein-free milk and also in McCollum's lactose. The 

 publication of Funk's work and his vitamin suggestions 

 set the investigators on a new trail. McCollum ob- 

 jected to the idea that his fat factor was Funk's vitamin. 

 Funk tried to show that the factor in butter fat was his 

 vitamin substance. The literature of 1912-1915 is full 

 of data bearing on this phase of the subject. Osborne 

 and Mendel were able to confirm the presence of a stim- 

 ulatory factor in certain fats as McCollum contended, 

 but still believed that their protein-free milk supplied 

 something else equally important. All the world 

 knows to-day that the truth was that two vitamins were 

 present. McCollum's butter fat did contain one, and 

 we now call it vitamin A, or fat-soluble A. The one 

 in his lactose and in the milk was proven to be appar- 

 ently the anti-beri-beri type, and to reconcile the no- 

 menclature it was listed as Funk's vitamin or "uniden- 

 tified dietary factory water-soluble B." 



By the time this tangle was ordered, the field of in- 

 vestigators had increased enormously and universal 

 recognition was now given to the idea that in addition to 

 nutrients of proper kind and quality, animals require 

 for their growth and maintenance at least two other 

 chemical substances hitherto unsuspected. It really 



