Karr 40 states that (hying at 100° C. does not affect the antineuritic efficiency of yeast, tomatoes or milk, but autoclaving at 120° C. for three to four hours leads to some destruction.

Miller (loc. cit.) found that carrots when tested by the Williams method had apparently suffered no loss of B when heated to 115° for 45 minutes. Whipple,41 using a modification of the same method, reported that cabbage had lost some but not all of its B on boiling for 30 to 60 minutes at 100° C. Davis42 states that while eight grams of raw potato supplies sufficient antineuritic to keep pigeons in good condition for 590 days an equal amount of either boiled or baked potato failed to give complete protection. Two grams of commercial dried potato gave no protection, but four grams had some protective power; though the experiment was not carried to its conclusion.

36 Davis, J. Home Ec. 12, 209, 1020.

37 Chick and Hume, J. Roy. Med. Corps, 20, 121, 1917; Emmett and Lurot, Proo. Soc. Biol. Chem. J. Biol. Chem. 41, vii, 1920. 38 Myers and Voegtlin, J. Biol. Chem. 42, 199, 1920. 39 Brill, Phil. J. Sci. 12, 199, 1917. 40Karr, J. Biol. Chem. 44, 255, 1921. 41Whipple, J. Biol. Chem. 44, 175, 1920. 42Davis, J. Home Ec. 12, 209, 1920.

With regard to the antineuritic vitamin found in animal products, Grijns 43 noted that exposure for one-half hour to 120° C. destroyed the antinueritic factor of buffalo meat, and Hoist44 found some loss of antineuritic power in beef after heating to 110° C. for half an hour. The destruction was more marked after exposure to 120° G. for an hour. Schaumann45 induced polyneuritis in dogs by a diet of horse flesh heated from one to three hours at 120° to 130° C, but Eijkman46 did not succeed in destroying the antineuritic power of horse flesh by heating to 120° C. for two hours.

According to Weill, Mouriquand and Michel 47 while an exclusive diet of raw, frozen or salted meat failed to produce nervous disorders due to nutritional deficiency, cats which had been given an exclusive diet of cooked meat succumbed with symptoms of inanition. Sterilised meat caused the appearance of nervous disorders after 35 to 39 days. Aging of the sterilized meat appeared to reduce the time required for such manifestations. Meat which had been sterilized and then kept 14 months caused nervous manifestations due to nutritional deficiency after 25 to 35 days. The symptoms were similar to, if not identical with, those produced in pigeons by feeding decorticated cereals.

Milk, at best, is not rich in the antineuritic factor and prolonged heating probably has a deleterious effect upon it. Stepp 48 suggested that the nutritive value of milk was somewhat lessened by boiling as it was necessary to use rather more boiled milk than raw to supplement a diet of bread which had been extracted with alcohol, but it is open to question whether this is due to destruction of the vitamin or to some other effect.49 McCollum and Davit50 found that whey from which the casein and albumin have been removed still possesses growth-promoting properties after heating to 120° for six hours, and would induce normal growth when fed at high level, and Osborne and Mendel51 were led to conclude from their own observations that: "We have no reason to believe that the nutrition-promoting properties of milk are lost by brief periods of heating." That prolonged heating at a high temperature may, however, cause serious deterioration of milk with respect to its antineuritic power is suggested by the work of Emmett and Luros52 who separated the vitamin from protein-free milk with fuller's earth53 and used this in the treatment of polyneuritic pigeons.

While 0.6 g. of the unheated material was unfailingly successful in promoting a cure, an equal amount of material which had been heated for six hours at 120° C. had no noticeable effect.

43 Grijns, Geneeak, Tidjachrift v. Ned. Int. 1901.

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

45 Scttftumaim, Arch. f. Schiffs. Trap. Hyg. Beihefte 3, 14, 1910.

46 Eijkman, Arch. f. Hyg. 58, 150, 1906.

47 Weill, Mouriquand and Michel, Coinpt. rend. soc. biol. 79,189, 1916. 48 Stepp, Ztach. Biol. 1911, 57, 135. 49See Ch.

50 McCollum and Davit, J. Biol. Chexn. 23, 247, 1915-16; Funk and Ma-callum, J. Biol. Chem. 27, 51, 1916; Bmmett and Lnroa, lb. 38, 257, 1919. 51 Osborne and Mendel, J. Biol. Chem 34, 541, 1918.

According to Chick and Hume 54 little antineuritic factor is likely to be present in canned and sterilized foods. Daniels and McClurg 55 disputed this on the evidence of their experiments in which normal growth was secured with young rats on a diet in which the only source of B was in the form of vegetables (soy or navy beans or cabbage) which had been cooked in a pressure cooker at 120° C. for 20 minutes, boiled in distilled water for 45 minutes, or boiled in a dilute alkali for 30 minutes. The various methods of treatment are said not to have appreciably affected the vitamin content. Their results are vitiated, however, by the fact that the heated vegetables were fed in large excess, the equivalents of 50 g. navy beans, 55 g. of soy beans, or 250 g. of cabbage for every 100 g. of dry food. McCollum, Simmonds and Pitz 56 found 25 g. of navy beans per 100 g. of dry food sufficient to supply the vitamin needed for normal growth, so the vitamin content of the vegetables might have been reduced by one-half in the above experiments without detection.

The effect of radium emanation on the vitamin B in yeast has been studied by Funk57 and by Suguira and Benedict58 Funk reported no loss of activity in the yeast extract with regard to either antineuritic or growth-promoting effect, after exposure to radium, but Suguira and Benedict disagree with him concerning the growth-promoting power, claiming that this factor may be partially inactivated by exposure to radium emanation. The reason for this discrepancy is not apparent.