Funk24 noted that inhibition of growth may be caused by a diet containing vitamin, and regarded this as indication that the growth-vitamin is not identical with the anti-beriberi vitamin. This conclusion was not justified, however, since the diet employed was undoubtedly deficient in A. Later25 he attempted to separate a growth-stimulating fraction from yeast by the methods which he employed for separating an antineuritic fraction. He states:

24 Funk, Z. Physiol. Chem. 88, 352, 1913.

25 Punk and MacaUum, J. Biol. Chem. 27, 63, 1916.

The fractionation of yeast with phosphotungstic acid shows that the growth-promoting substance is carried down with the precipitate and a large part of its activity is lost during the fractionation. The instability of this substance when fractionated with silver salts presents greater difficulty than that experienced during the fractionation of the beriberi vitamin. . . . The experimental evidence indicates that considerably larger quantities of vitamins are necessary for stimulating growth than for curing beriberi, and the losses occurring during fractionation are more apparent in the former than in the latter case. However, it must be admitted that while it is uncertain whether these two substances are chemically different, the results obtained do not exclude such a possibility. Lloyd's reagent, as recommended by Seidell, has also been used as a precipitant without much success, as rats which have been given the filtrate have also shown increments in growth.

All attempts to distinguish between the two substances by their behavior towards precipitants have proved a failure. While the two seem to be precipitated by the same reagents, the loss of activity in the course of manipulation is so large that no satisfactory conclusions can be reached.26 Mitchell 27 points out that the growth-promoting factor appears to suffer more extensive deterioration during fractionation than does the antineuritic, which may be regarded as an indication of the existence of two substances instead of one, although it can hardly be considered a conclusive argument. Drum-mond remarks that it is naturally very difficult to trace the growth-promoting principle during fractionation, because minute traces of that substance do not always demonstrate their presence by causing appreciable increase in the body weight of the experimental animal, whereas such extracts are often sufficient to cause decided improvement in the condition of a polyneuritic pigeon.28

Both the antineuritic and the growth-promoting factors are soluble in water and dilute alcohol. According to Osborne and Mendel29 and Drummond,30 the growth-promoting factor of yeast is insoluble in absolute alcohol. The antineuritic, on the other hand, is said to be extracted by strong alcohol from the foodstuffs containing it.31 While acetone and benzene extracts of fat-free wheat embryo are as efficient as water or alcohol in curing polyneuritis, these solvents are not successful in extracting the growth-promoting B from foodstuffs.32

26 see Punk and Macallum, 1. c; Eddy, J. Biol. Chem. 27, 113, 1916; Drummond, Bioch. J. 11, 255, 1017.

27 Mitchell, J. Biol. Chem. 40, 399, 1919.

28 Drummond, Bioch. J. 11, 255, 1911.

29 Osborne and Mendel, J. Biol. Chem. 31, 149, 1917.

30 Drummond, Bioch. J. 11, 261, 1918.

31 Eijkman, Arch. f. path. Anat. 148, 523; 149, 197; Fraaer and Stanton, Lancet, 1910, ii, 1755; Funk, J. Physiol. 43, 395, 1911-12; Cooper, J. Hyg. 12, 436, 1913. 32 McCollum and Kennedy, J. Biol. Chem. 24, 491.

These facts would seem to indicate the existence of two factors, but there are sufficient discrepancies in the statements as to solubility, even where there is no question of more than one vitamin being involved, to make us chary of drawing conclusions from this property.33

The stability of the two towards acids and alkalies seems on the whole to be very similar. Williams and Seidell34 have reported an experiment in which they found that when fuller's earth, which had been activated by contact with autolyzed yeast filtrate, was treated with aqueous alkali it lost its growth-promoting power, whereas its antineuritic efficacy was unchanged. Emmett and McKim,35 however, found that even without the alkali treatment, activated fuller's earth had very little effect in promoting the growth of pigeons, being very inferior to the natural foodstuffs in this respect. They conclude that the outer layers of the rice grains contain two vitamins, one of which cures or prevents polyneuritis and the other produces growth, and of these two the yeast vitamin preparation obtained with fuller's earth contains chiefly the curative fraction.

Somewhat more convincing evidence has been obtained from a study of the relative stability of the two towards high temperatures. This has been very carefully investigated by Emmett and his coworkers, from whom the accompanying table summarizing the results of earlier investigators has been taken.36

33 McCollum and Davis, J. Biol. Chem. 23, 229, 1915; McCollum and Simmonds, Ibid. 33, 56, 1918.

34 Williams and Seidell, J. Biol. Chem. 26, 432, 1916. 35 Emmett and McKim, J. Biol. Chem. 32, 409, 1917. 36 Emmett and Luros, J. Biol. Chem. 43, 265, 1920.

Polyneuritis (Antimeuritic Vitamin)

† a, tested ouratrvely by giving it to polyneuritic fowl; b, tested prophylac-tically by feeding normal fowl.