Since the term amine has a certain definite significance in organic chemistry, which is not intended to apply in vitamine, Hopkins has suggested the term "accessory food substances" instead, a usage which is followed by many English writers. McCollum objects to this terminology however on the ground that "accessory" has a connotation of "dispensable" while the substances referred to are essentials, and made the suggestion that the growth-promoting substance present in butter-fat should be designated "fat-soluble A" and the anti-beriberi substance "water-soluble B" because of their respective solubili-ties in fats and in water respectively. A new term "advitants" has: recently been introduced as a substitute for "vitamines," but it remains to be seen whether or not it will find general acceptance.2 In the present work the nomenclature adopted is that suggested by Drummond,3 according to which the final "e" of vitamine is dropped,3a thus avoiding the objectionable "amine" termination, while retaining a name that has become familiar through long usage.3b The different classes of vitamins are distinguished as A, B, and C.

A third member has been added to the vitamin class, the "C" or scurvy-preventing vitamin, which is the substance long known to be present in lemon-juice and which acts as a preventive or cure for scurvy. Whether or not we shall ultimately recognize the existence of still other vitamins cannot at present be confidently predicted. There is already certain evidence which would seem to indicate the possibility of two distinct substances at present classed together as "vitamin B," one of which functions as a beriberi preventive while the other is of importance in growth, but so far the evidence is inconclusive. This question will however be dealt with in more detail in a later chapter.

It may be asked, how can the existence of a whole class of substances of fundamental importance in the nutrition not only of man but of all animals have so long escaped observation? The explanation is based partly on the wide distribution of the vitamins in natural foods and partly on the minute quantities required to maintain an animal in at least comparatively good health. Under ordinary conditions, even on what would be considered a most restricted diet, traces of vitamins are always present and these traces are sufficient to prevent obvious disease, although it is probable that many cases of abnormality, debility, and general lack of tone, if not actual disease, will be found attributable to lack of sufficient vitamins in the diet. It is only when a food has been so treated as to remove or destroy the vitamins naturally present that the results become so evident as to force themselves upon the attention. By an unfortunate perversity the present day manufacturer not infrequently endeavors to make his products more attractive by processes which seriously reduce the vitamin content, and hence the nutritive value, as in the treatment of cereals when the vitamin-rich germ and cortex are removed, or in the overheating of foods when drying for the purpose of preservation.

A striking illustration of the result of this is seen among the rice-eating people of the Orient where beriberi followed the introduction of modern milling machinery by which the germ and "silverskin" of the rice grain, and in these the whole amount of vitamin B, is removed. In the West the food is more varied, and it is unlikely that any diet would not contain a certain amount of all three vitamins; whether the amount is always adequate is however open to serious question.

2 J. Chem. 800. 1920, 117, 1201.

3 Drummond, Bioch. J. 14,600, 1920.

3a Funk does not endorse Drummond's proposal to drop the final "e" in the term "vitamine." (J. Ind. Eng. Chem. 1921, 1110).

3b The word vitamin has been pronounced in a variety of ways, the approved pronunciation being vy'-ta-meen.

A second reason why the vitamins escaped detection so long is because their absence is indicated only by a subnormal condition which may usually be ascribed to other causes. Ordinarily, lack of vitamin will be accompanied by other unfavorable conditions; moreover the morbid state of the organs which resulted from vitamin deficiency might easily be regarded as the cause, instead of merely one of the symptoms of malnutrition.

Finally, there is the wide-spread tendency to look for a positive rather than a negative cause of disease; for the presence of an actively injurious substance rather than the absence of an essential nutritious element. It was only when carefully conducted feeding experiments were carried out with healthy animals kept under ideal conditions in every respect save the one under investigation, that failure of health could be traced to its true source.

How the vitamins act, what part they play in the life process, we cannot say definitely. When we have described their general functions - growth-promoting, beriberi- and scurvy-preventing - and their distribution, and have emphasized their indispensability, we have said, almost all that we know positively. Small, even minute amounts are surprisingly effective, a fact which suggests that they are of the nature of catalysts, agents which have the power of bringing about extensive chemical change without being themselves altered in the process. Practically all of the complex reactions in the living cell are believed to be brought about by the catalytic action of the enzymes present in the cell, and it would not be difficult to imagine an essential r61e for certain catalysts which do not exist pre-formed in the organism but must be obtained from the food. On the other hand, the degenerative change in the vital organs, particularly the ductless glands, would suggest the possibility of an intimate connection between the vitamins and the internal secretions.

They may be hormones, that is, stimulants in the absence of which the glands fail to produce the normal secretion, or possibly they may be essential though almost infinitesimal constituents of certain tissues, which cannot be synthesized in the animal body, and without which those tissues cannot develop.

Such evidence as we have on these points will be given in a later chapter.