FOODS — HUMAN NUTRITION. 561 



fact that even more of this substance has been obtained from lard than from 

 butter. 



" So far as our experience has shown, the addition of butter fat to our 

 natural * protein-free milli ' foods gives them an efficiency quite comparable 

 with that of our milk food in promoting recovery and the completion of 

 growth. The exact chemical differences between the adequate butter fat and the 

 Inadequate lard (which determine success and failure respectively in the food 

 mixtures employed) are far from being satisfactorily known. Chemical ex- 

 amination of the butter fat indicates that the effective component is not a 

 phosphatid or any inorganic substance, inasmuch as nitrogen, phosphorus, and 

 ash are lacking in the product employed. It is suggestive to note that in the 

 one case (lard) we are dealing essentially with a fat mixture deposited in 

 storage depots of the animal organism ; in the other, the butter fat represents 

 the product of metabolic activity and synthesis on the part of the cells of the 

 mammary gland. What, if anything, this distinction between cellular product 

 and reserve fat may mean physiologically, remains to be investigated. 



" The researches which have been devoted in recent years to certain dis- 

 eases, notably beri-beri, have made it more than probable that there are con- 

 ditions of nutrition during which certain essential, but, as yet, unknown sub- 

 stances must be supplied in the diet if nutritive disaster is to be avoided. 

 These substances apparently do not belong to the category of the ordinary nu- 

 trients, and do not fulfill their physiological mission because of the energy which 

 they supply. Funk [E. S. R., 28, p. 261] has proposed the name vitamin for 

 the type of substance thus represented. 



" Without minimizing the importance of the new field of research and the 

 new view points in nutrition which are presented by these recent findings, we 

 may nevertheless hesitate to accept the extreme generalizations which have 

 already been proposed on the basis of the evidence obtained largely from the 

 investigation of pathological conditions. ... It is still rather early to gen- 

 eralize on the role of accessory * vitamins ' when the ideal conditions in respect 

 to the familiar fundamental nutrients and inorganic salts adequate for pro- 

 longed maintenance are not completely solved. Speculation is quite justifiable 

 in so far as it directs attention to a new phase that needs to be taken into 

 account. 



" Funk has expressed the belief that the substance which promotes growth 

 and must be present in order to avert the cessation of growth, which we have 

 described to occur after a certain period of successful growth on our earlier 

 dietaries, is either identical with, or analogous to, the * vitamin ' which plays 

 the role of an antiscorbutic substance. For this we can as yet find no com- 

 pelling evidence. Certainly the nitrogen-free butter fat, so successful in reme- 

 dying our growth failures, contains no substance chemically related to the 

 nitrogenous products which have lately been credited with this unique physio- 

 logical efficiency. . . . 



" Butter fat has shown a further interesting nutritive superiority over lard. 

 At certain periods of the year, particularly in summer months, we have fre- 

 quently failed to secure satisfactory growth on the dietaries which proved 

 adequate during the usual period of 60 to 100 days at other seasons. Occasion- 

 ally young rats in the stock colony have exhibited a similar ' epidemic ' of 

 poor growth at the same season. The failures are, however, not common to 

 rats fed on the milk food; and w^e have lately observed that the seasonal 

 failure is also averted by the addition of butter fat to the usual ' protein-free 

 milk ' food mixtures. Again, another type of nutritive deficiency exemplified 

 in a form of infectious eye disease prevalent in animals inappropriately fed is 



