Commenting on the lack of uniformity in the observations reported from different sources, Steenbock and Boutwell25 conclude that the data of the different investigators in this field are substantially true to fact and that the variance of opinion is due to a failure to appreciate that the reaction of destruction may be one of low velocity impeded or accelerated by secondary factors. For example, in a ration containing twice as much vitamin as necessary for normal growth no evidence of its destruction would of course be obtained even though one-half of the amount present might have been destroyed by the treatment. In addition, there is no doubt, according to Steenbock and Boutwell, that there obtains a great difference in the stability of the vitamin as found in different materials.

The antineuritic vitamin appears to be somewhat less stable than the vitamin A. Its presence in dry grains and other dried foodstuffs shows that it can withstand desiccation, and there is much evidence to indicate that heating at the temperature and for the length of time ordinarily employed in the cooking of food produces comparatively little if any destruction of the antineuritic properties, but at temperatures above 100° C. the rate of destruction appears to increase rapidly. Observations to this effect were recorded by some of the earlier observers, although their experiments were not carried on quantitatively. Grijns 26 showed that one-half hour's exposure to 120° C. destroyed the antineuritic power of unmilled rice and " Kat-jang idjo" beans. Eijkman27 found that seeds which had been heated from 115 to 135° for two hours had little protective action against polyneuritis. Hoist28 reported that dried peas and unpeeled barley did not lose their antineuritic power on heating to 115° for half an hour.

Weill and Mouriquand29 found that barley, rice and maise which had been heated for an hour and a half at 120° no longer possessed any antineuritic property, and Emmett and Luros 30 report that while heating for 120° for one hour had no effect on the antineuritic power of unmilled rice it was partly destroyed at the end of two hours and completely destroyed in six hours, and that the vitamin was still less stable to heat after it had been extracted from its natural source. Curiously, rice which has completely lost its antineuritic power was still able to promote the growth of young rats. Braddon 31 states that persons eating parboiled rice did not contract beriberi provided the pericarp had not been removed by one boiling.

21 Campbell and Chick, Lancet 1919, ii, 320.

22 Hopkins, Brit. Med. J. 1919, ii, 147.

23 Drummond and Coward, Biochem. J. 14, 661, 1920.

24 Steenbock, Sell, Nelson, and Buell, Proc. Soc. Biol. Chem. J. Biol. Chem. 46, XXXII, 1921.

25 Steenbock and Boutwell, J. Biol. Chem. 41, 164, 1920.

26 Grijns, Geneesk, Tydschrift. v. Ned. Ind. 1901. 27 Eijkman, Arch. f. Hyg. 68,160, 1906.

In a carefully conducted experiment by Chick and Hume32 the antineuritic property of wheat embryo as tested by its curative effect on polyneuritic pigeons was unaffected by heating to 100° C. for two hours; after 40 minutes at 113° its curative effect was reduced by one-half, and after two hours at 118° to 124° the antineuritic activity was less than one-fourth that of untreated material.

McCollum and Davis33 reported that heating to 120° for one hour did not injure the growth-promoting properties of wheat embryo, but their results are open to the criticism that the wheat embryo was fed at too high a level (13 per cent of the diet) to show whether partial destruction had taken place, since they themselves had found that two per cent of unheated wheat embryo was sufficient to induce normal growth. McCollum, Simmonds, and Parsons 34 found that peas which had been cooked under 15 pounds pressure for an hour and a quarter and then dried in a current of hot air when fed to the extent of 25 per cent of the diet provided enough B to enable young rats to grow at normal rate to full adult size, but here again the amount fed was probably far above the minimum and considerable destruction may have escaped notice.

Miller,35 using the Williams yeast test for B, calculated that by boiling navy beans for 30 minutes at 120° a loss of 40.6 per cent of the growth-promoting power was brought about and that practically the same loss (37.5 per cent) was brought about by boiling in 0.5 per cent sodium bicarbonate solution for one hour and ten minutes. Davis 36 found that seeds suffered a complete loss of B on heating for two and a half hours to 120° C, although at the end of 35 minutes at this temperature there was sufficient vitamin left to keep pigeons in good condition for 280 days.

28 Hoist, J. Hyg. 7, 619, 1907.

29Weill and Mouriquand, C. r. soc. biol. 78, 649; 81, 432, 1918.

30 Emmett and Luros, J. Biol. Chem. 43, 265, 1920.

31 Braddon, "The Cause and Prevention of Beriberi." London, 1907.

32 Chick and Hume, Proc. Roy. Soc. 90 B, 66.

33 McCollum and Davis, J. Biol. Chem. 23, 191, 247, 1915.

34 McCollum, Simmonds and Parsons, J. Biol. Chem. 37, 287, 1919.

35 Miller, J. Biol. Chem. 44, 159, 1920.

It seems clear, therefore, that so far as grains and pulses (peas and beans) are concerned the B vitamin is unquestionably destroyed by heating to 115° to 120° for one to two hours, while deterioration is much slower at 100° and may therefore be inconsiderable in the course of ordinary cooking.

Yeast is affected in much the same way, a temperature of 120° bringing about complete destruction of the vitamin content in two hours, while 100° seems to be ineffective.37 The yeast vitamin seems to be less stable when separated from the yeast plant than when in situ, since Myers and Voegtlin38 found that the active precipitate from autolysed yeast becomes inactive on drying at room temperature. In this connection it may be noted that Brill found the vitamin content of hydrolyzed extract of rice polishings to deteriorate somewhat with age.89