MISCELLANEOUS WATER-SOLUBLE GROWTH FACTORS 



anaemia, when maintained on a purified diet supplemented by 

 aneurine, riboflavine, nicotinic acid, pyridoxine and pantothenic acid ; ^° 

 the anaemia was cured by extracts of yeast, liver or rice bran. Pigeons 

 have also been said to require a weight restoration factor (page 6ii). 



The inference underlying all this work is, of course, that new 

 factors essential for the well-being of animals, and distinct from the 

 known members of the vitamin B complex are present in the supple- 

 ments used to relieve the deficiency symptoms. It will be noted that 

 in most instances, the material used as the supplement was an extract 

 prepared from either liver or yeast, both of which, as already noted, 

 are excellent sources of most members of the vitamin B complex. In 

 none of this work, however, was any serious attempt made to isolate 

 and purify the responsible factor. Such attempts have been made 

 with certain other factors, however, and the concentrates so obtained 

 h-ave been shown to produce the same effect in animals as the original 

 crude extracts. Many of these concentrates, although still relatively 

 impure, have been given specific names, some implying that the 

 active principle is a vitamin or even a member of the vitamin B 

 complex. 



Claims for the isolation of a new vitamin have often rested on 

 very flimsy evidence, because the preparations originally obtained 

 have been highly impure and no subsequent attempts have been made 

 to purify them, much less to isolate the responsible factor in the pure 

 state. For this reason many of the older " vitamins " are now to be 

 regarded as of historical interest only (see page 613), although many 

 factors described in the recent literature merit more serious attention 

 and may ultimately achieve recognition as vitamins. These are 

 factors now under active investigation, which appear to have a reason- 

 able chance of being isolated in the pure state. Once this has been 

 done their biological properties can be examined to confirm that the 

 activity supposed to be characteristic of them really is a function of 

 the pure substance and not of an impurity from which it has previously 

 not been separated. 



It is felt that a brief account of the factors to which specific names 

 have been given is necessary to make this survey complete, whether 

 the factors belong to the group that is now only of historical interest 

 or whether they are strong favourites for ultimate recognition as 

 members of the vitamin B complex. 



References to Section 2 



1. E. R. Norris and J. Hauschildt, Science, 1940, 92, 316. 



2. K. Schwartz, Z. physiol. Chem., 1942, 276, 232, 



3. A. E. Schaefer, J. M. McKibbin and C. A. Elvehjem, /. Nutrition, 



1942, 23, 491. 



610 



