However, recent investigations pointing to the stability of vitamins toward heat, in the absence of air or oxidizing agents, suggest other causes than heat alone. It is not unlikely that the catalytic action of the nickel catalyzer may be exerted on the vitamins thereby changing their character.15a Fahrionl5b refers to the therapeutic value of cod liver oil due to vitamins. Oil extracted by cold pressing contains the vitamins in a potent state. He notes, however, that the oil obtained by solvent-extraction does not contain these food factors. As has been stated, refining by alkali destroys vitamins. Fuller's earth probably absorbs vitamins during the bleaching operation.

It follows that lard substitutes made from refined vegetable oils which have been thickened to the consistency of lard by the addition of 15 or 20 per cent of hydrogenated oil, scarcely can be expected to contain vitamins. Various suggestions have been made for adding to oleomargarine and compound lard suitable extracts of vitamin A.15 e The result of the investigations of Halliburton, Drummond and others on the absence of vitamins in processed vegetable oils have led to much controversy over the relative merits of animal and vegetable fats, of milk and butter, oleomargarine, vegetable oil, compound lard etc. Richardson15d takes issue with the champions of the virtues of milk and butter. With a varied diet, he believes that it makes no difference whether oleomargarine or butter, in fact any dairy product, is consumed.

13a Steenbock, Sell and Buell, J. Biol. Chem. 47, 89, 1021.

14 See Bills, Hydrogenation of Oils, New York, 1919.

15 Halliburton, Paton, Drummond and others, J. Physiol. 1919, 53, 335. 15a See Drummond, J. S. C. I., 1921, 81 T.

15b Chem. Umahau, 1920, 97 and 110.

If rats, the experimental animals most used in the past for dietetic experiments, are fed a mixed ration of moderate variety, consisting of the food commonly used on the ordinary table, meat, vegetables, grains and fruits, but without milk or dairy products, they get along very well indeed, without developing dietary or deficiency diseases, showing normal growth and health, except for an occasional ailment or infection to which such laboratory animals are always subject. Such rats reproduce unto the nth generation in spite of the absence of their per diem of milk. When to such a diet either oleomargarine or butter is added no noteworthy change results which, Richardson notes, is as might have been foreseen and expected. Rabbits and guinea pigs grow to maturity, flourish and reproduce on green things as do the large herbivorous animals, while the carnivorous kinds eschewing vegetable products subsist entirely on meat. These would commonly be considered to be most unbalanced diets, but the addition of dairy products does not change the course of nature.

Large quantities, however, might and sometimes do cause serious disorders, since milk and dairy products are very different in some of their properties from the natural foods of certain animals.

Osborne and Mendel 16 claim that the centrifuged butter-fat from which they obtained the growth-promoting factor contained neither nitrogen nor phosphorus. This was doubted by McCollum and Davis,17 but confirmed by the analyses of Folin and of Funk and Macallum,18 who found only 0.0003 per cent of nitrogen, and of Osborne and Wakeman,19 who estimate the phosphorus content of the butter oil in which the growth-promoting principle is concentrated at 0.0006 per cent. In view of these figures it seems impossible that either phosphorus or nitrogen should form a constituent part of the fat-soluble vitamin.

15 c Experiments made in the laboratory of the senior author by adding an extract of alfalfa to oleomargarine (nut butter) were not very promising owing to the foreign flavor imparted to the product.

15 d Richardson, Am. Food Jour., July, 1921.

16 Osborne and Mendel, J. Biol. Chem. 20, 382, 1915.

17McCollum and Davis, J. Biol. Chem. 19, 250, 1914.

18 Funk and Macallum, Zeitsch. f. physiol. Chem. 92, 13, 1914.

19 Osborne and Wakeman, J. Biol. Chem. ax, 91, 1915.

Normal growth and reproduction has been observed in albino rats, a species of animal in which there is a complete absence of carotinoid pigments, with ewe milk-fat and carotinoid-freel egg yolk as the sole sources of fat-soluble vitamin. The ewe milk-fat contained only 0.00014% of carotin and the ration showing the best results contained only 0.0000126% of carotin. The basal ration used was entirely devoid of carotinoids. A quantitative comparison of the carotin content and vitamin efficiency of various rations shows no relationship. Carotinoid pigment is not necessary for the normal growth and reproduction of albino rats and apparently the fat-soluble vitamin and carotinoid pigment are not identical.19a.

The antineuritic or water-soluble B vitamin is, as the name implies, generally regarded as soluble in water20 but Cooper21 found that the antineuritic content of meat is not extracted by water although it is readily soluble in alcohol, after which it becomes soluble in water. From lentils B can be extracted directly by water.22 Suguira 23 prepared a sparingly soluble compound from yeast which had antineuritic properties. It would seem that the antineuritic, like the fat-soluble vitamin, may vary in solubility according to the condition in which it is found. Many observers24 have reported its solubility in ethyl alcohol, and this is commonly used as an extractive. Osborne and Mendel25 have pointed out that the term alcohol is sometimes rather carelessly used, without specifying whether absolute or dilute alcohol is referred to. They state that in their experience absolute alcohol is by no means an adequate solvent for the antineuritic vitamin and that the solubility in dilute alcohol depends on the amount of water present.

This is confirmed by Drummond 26 and by Osborne, Wakeman and Ferry.27