The existence of three well-defined vitamins, growth-promoting A, antineuritic B, and antiscorbutic C, is apparently well established. Some evidence has been accumulated which points to the possibility of a fourth, which has usually been included with the antineuritic factor on account of similarity of properties, but which is distinguished from this inasmuch as it is essential for growth but has neither preventive nor curative effect on polyneuritis.

Assuming, in the latter case, that we are dealing with two distinct factors, it will be noted that they show striking uniformity of distribution. Although our present methods of investigation are not sufficiently standardized to make quantitative results entirely convincing, in general it would appear as though foodstuffs which are rich in antineuritic are also rich in growth-promoting power, and those low in antineuritic are also poor in the growth-promoting factor. There are, however, several instances in which this fails to hold true. While a diet containing 88 per cent of unhusked rice, along with casein, salts, and butter-fat, is said to furnish sufficient B for normal growth, being comparable to whole wheat in this respect,1 Gibson and Concepcion 2 report that an exclusive diet of unhusktid rice afforded incomplete protection to pigeons against polyneuritis, as was shown by the degenerative changes in the sciatic nerve. Voegtlin, Lake and Myers3 found the endosperm of corn and wheat practically devoid of antinueritic while Osborne and Mendel 4 assert that wheat endosperm is rich in growth-promoting B. According to Chick and Hume, the onion is poor as a source of antineuritic factor, being about equivalent to fresh meat in this respect,5 and Chamberlain, Vedder and Williams6 report the water extract of onion to be without effect on polyneuritic pigeons; on the other hand,Osborne and Mendel7 found considerable amounts of growth-promoting B present.

Chick and Hume (1. c.) place carrots in the same class with onions and fresh meat as a source of antineuritic factor, and Davis 8 found that five grams per day afforded no protection against polyneuritis, yet Osborne and Mendel 9 and Suguira and Benedict10 agree that they are rich in growth-promoting B. Very similar evidence is given with regard to the potato. While comparable to carrots in growth-promoting power,11 it is low in antineuritic factor,12 although Davis13 secured protection against polyneuritis by administration of eight grams of raw potato per day. Milk is poor in antineuritic substance, according to Chick and Hume14 and also Gibson and Concepcion,15 but remarkably rich in growth-promoting power, according to Hopkins.16 Although other investigators have not succeeded in attaining normal growth with such extremely small quantities of milk as those used by Hopkins, they have demonstrated the presence of at least a fair amount of growth-stimulant. Orange juice is said to contain antineuritic factor in very small amounts,17 but Osborne and Mendel18 found it almost equivalent to milk in growth-promoting power and Funk and Dubin,19 using a modification of Williams' yeast test, assert that it has about half the value of autolysed yeast as a growth stimulant.

Several observers have noticed considerable difference in the relative amounts of the same foodstuff which are required to protect against polyneuritis and to induce growth. Schaumann20 ascertained that if a ration of a vitamin-containing foodstuff were adequate to prevent onset of polyneuritis in birds, when this ration was added to a diet of polished rice, loss of weight was prevented. On the other hand, extracts of these foodstuffs prepared by extraction with acid or alcohol, while still sufficient to prevent polyneuritis, were no longer able to prevent loss of weight.

1 McCollum and Davis, J. Biol. Ghem. 23, 206, 1915. 2 Gibson and Concepcion, Phil. J. Sci. 9 119, 1914. 3 Voegtlin, Lake and Myers, Proc. Soc. Biol. Ghem., J. Biol. Ghem. 41, x., 1920.

4 Osborne and Mendel, J. Biol. Ghem. 37, 557, 1919.

5 Chick and Hume, TV. Soc Med. Hyg. 10, 141, 1916-17.

6 Chamberlain, Vedder and Williams, Phil. J. Sci. B7, 45, 1912.

7 Osborne and Mendel, J. Biol. Chem. 39, 29, 1920.

8 Davis, J. Home Econ. 12, 209, 1920.

9 Osborne and Mendel, J. Biol. Chem. 41, 451, 1920.

10 Suguira and Benedict, J. Biol. Chem. SB, 171, 191, 1918.

11 Osborne and Mendel, J. Biol. Chem. 41, 451, 1920; McCollum, Sim-monds and Parsons, lb. 36, 197, 1918.

12 Chick and Hume, Med. Res. Com. Report, No. 88, p. 30; Vedder and Clark, Phil. J. Sci. B. 7, 423; McCollum and Kennedy, J. Biol. Chem. 24, 491, 1915-16.

13 Davis, J. Home Econ. 12, 209, 1920.

14 Chick and Hume, Jour. Roy. Army Med. Corps, 29, 121, 1917.

15 Gibson and Concepcion, Phil. J. 6ci. 11, 119, 191.

16 Hopkins, J. Physiol. 44, 425, 1912; Hopkins and Neville, Bioch. J. 7, 97, 1913.

17 Harden and Zilva, Bioch. J. 12, 93, 1918.

18 Osborne and Mendel, J. Biol. Chem. 42, 465, 1920.

19 Funk and Dubin, J. Biol. Chem. 44, 492, 1920.

20 Schaumaim, Trans. Soc. Trop. Med. Hyg. 5, 59, 1911.

Voegtlin and Towles21 noted that the extracts of autolyzed spinal cord may be antineuritic, yet be unable to re-establish normal metabolism, i. e., restore body weight. Cooper came to the conclusion that the substances preventing polyneuritis and maintaining weight were separately distributed in natural foodstuffs, since for certain of these, in which the two appeared to be evenly balanced, such as yeast, ox-heart, and ox-brain, the daily ration required to prevent polyneuritis also maintained the weight of the bird, while in others, such as egg-yolk, barley, lentils, this daily ration had to be increased if loss of weight were to be prevented. Chick and Hume22 observed that while three grams of wheat germ every second day prevents polyneuritis, two to three grams, daily produced great improvement in body weight, health, and vitality.23 These results might be interpreted either as due to different requirements of the same vitamin for different metabolic functions or to two vitamins which are present in different amounts. The evidence is not convincing on either side. Mitchell (1. c.) remarks: In investigations on the comparative antineuritic properties of foods, the experimental polyneuritis of pigeons is almost invariably induced by a diet of polished rice.

Polished rice is defective in several factors beside the antineuritic. It is therefore probable that foods containing comparable amounts of this vitamin may be unequally effective in preventing or curing the polyneuritic symptoms, depending upon the extent to which they supple-' ment polished rice in these other respects. Conversely, foods containing unequal concentrations of the antineuritic principle may have their relative values as sources of the vitamin distorted for the same reason.

21 Voegtlin and Towles, J. Exp. Pharmocol. 5, 67, 1913.

22 Chick and Hume, Proc. Roy. Soc. 90B, 44.

23 Chick and Hume, Proc. Roy. Soc. 90B, 44.