On page 136 there is a sentence which reads that "the consensus of opinion is that fat-soluble A is a vital factor in health, and that its absence in a diet is one of the causative factors in the development of rickets." This statement needs little modification. It must, however, be stated that almost all of the workers on the relation of vitamine A to rickets, whose results have been published during the past year, assail Mellanby's view that the absence of vitamine A is the sole cause of rickets though none of them deny that the absence of this vitamine, particularly in young animals, brings on disease and ultimate death.

The work of Sherman and Pappenheimer at Columbia, and of McCollum, Howland and Kramer at Johns Hopkins, has shown that both calcium and phosphorus, and particularly the latter, play an important role in this disease. One might have anticipated some such finding as this, for is not the disease associated with a non-development of the bony structure, and are not bones largely composed of calcium phosphate?

The more exact micro-chemical methods for the determination of various substances in blood have made it possible for Howland to show that in rickets the phosphorus content of blood is subnormal; and that further, upon recovery by the administration of cod liver oil, the amount of phosphorus in the blood increases until the normal figure is reached. This is of the utmost diagnostic value.

We may summarize the matter by saying that though the exact etiology of rickets has yet to be discovered, it seems clear that vitamine A, phosphorus and calcium all play a role. As Prof. McCollum puts it: "The results do not in our opinion exclude the fat-soluble A from consideration as an etiological factor in the production of rickets and kindred diseases, since the level of the blood phosphate (a salt of phosphorus) is, in all probability, determined in part by the amount of the fat-soluble A available for the needs of the organism" {References: A. F. Hess, Journal of the American Medical Association, volume 76, page 693, 1921; A. F. Hess, etc., Journal of Biological Chemistry, volume 47, page 395, 1921; H. M. M. Mackay, Biochemical Journal, volume 15, page 19, 1921; E. V. McCollum, etc., American Journal of Hygiene, volume 1, page 492, 1921, and the Johns Hopkins Hospital Bulletin, volume 32, page 160, 1921; H. C. Sherman and A. M. Pappenheimer, Journal of Experimental Medicine, volume 34, page 189, 1921; J. Howland and B. Kramer, American Journal of Diseases of Children, volume 22, page 105, 1921).

The Value of Cod Liver Oil in Rickets, Cod liver oil as a cure for rickets has been known and used for many years, though for a long time it was regarded as a "tonic and nutrient." In 1914 Drs. Osborne and Mendel showed that the oil is rich in vitamine A, and very recently Zilva, of the Lister Institute, has claimed that the crude oil is 250 times as rich in vitamine A as is butter fat. This would naturally lead to the supposition that rickets and fat-soluble A are very intimately related. However, the case is by no means a clear-cut one, as the previous paragraph has already indicated. Further, Drs. Hess and others have shown that milk, rich in fat-soluble A, does not always prevent rickets, whereas cod-liver oil invariably does; and the oil is a very specific cure too. It does not seem likely that the difference between cod liver oil and any other fat is merely one of difference in quantity of fat-soluble A.

Another factor that differentiates cod liver oil from other fats is one that we have already indicated, namely, that the oil always causes calcium retention in cases of rickets; whereas milk, for example, does not.

Dr. Hess writes very pertinently: "There are approximately 125,000 children in New York City between the ages of 3 and 15 months, the period of greatest susceptibility to rickets. If we estimate generously that the families of one-third to one-quarter of these children are unable to purchase cod liver oil, and if we agree that the development of rickets may be prevented by giving a teaspoonful three times a day, then, at the present cost, rickets could be practically abolished in this city by the expenditure of about $ 100,000 a year. This is but one of many instances in which the community does not get the full benefit of our medical knowledge" (References: A. F. Hess, Journal of the American Medical Association, volume 76, page 693, 1921; E. A. Park and J. How-land, Johns Hopkins Hospital Bulletin, volume 32, page 431, 1921; P. G. Shipley, E. A. Park, E. V. McCollum, N. Simmonds and H. T. Parsons, Journal of Biological Chemistry, volume 45, page 343, 1921; L. B. Mendel, New York State Journal of Medicine, volume 20, page 212, 1920; S. S. Zilva and M. Miura, Lancet, volume 1, page 323, 1921). Xerophalmia and Vitamine A. The opinion expressed by McCollum (page 128; also pages 207 and 209) that the peculiar eye disease known as xerophalmia or keratomalacia is due to a lack of vitamine A (fat-soluble A) has been confirmed. Drs. Osborne and Mendel give the following instructive table:

Dr. Emmett fully confirms these results, as his own table shows:

Hence the theory, still held by some, that xero-phalmia is due to an infection, is untenable.

Dr. Emmett further points out that "all attempts to transmit the disease by using sterile threads of gauze, passing them cautiously over the edge of the lids of the sore eyes, and then carefully inoculating the eyes of the other rats "failed." Treatment of advanced cases of sore eyes with a saturated boric acid and also with a silver protein solution failed to relieve the condition. However, when as little as one to two per cent of an extract containing the so-called fat-soluble A vitamine was added to the ration, the eyes were speedily cured and the rats increased in weight, indicating that this extract was a specific cure for xerophalmia." (References: T. B. Osborne and L. B. Mendel, Journal of the American Medical Association, volume 76, page 906, 1921; I. M. Wason, Journal of the American Medical Association, volume 76, page 908, 1921; A. D. Emmett, Science, volume 52, page 157, 1920.