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NA TURE 



[July 29, 1922 



favourable; rickets may be encouraged (a) by defective 

 diet ; the deficiency being in the sense of (i.) too little fat- 

 soluble A, (ii.) too little calcium and phosphate, (iii.) too 

 little meat and too much bread ; (b) by bodily confine- 

 ment and lack of exercise or by rapid growth ; or (c) by 

 the absence of sunlight. Conversely, rickets may be 

 ameliorated or cured by (a) giving plenty of fat-soluble 

 vitamin in cod-liver oil or butter, avoiding too much 

 cereal food, and (which is of experimental rather than 

 practical importance) having a reasonable amount of 

 calcium and phosphorus in the diet ; (b) by encouraging 

 metabolism by massage and electricity, or, which comes 

 to the same thing, by being careful that the total intake 

 of energy in the food is no more than is necessary ; 

 or (t) by exposing the skin to open sunlight or to 

 sources still richer in ultra-violet light, such as mercury 

 vapour lamps or metallic arcs. 



Dr. Findlay rightly objects to any superficial con- 

 clusion from this array of circumstances that rickets 

 has many causes. A disease of so definite and isolated 

 a species must be held prima facie to have but one 

 cause. What that vera causa is we do not know, 

 but evidently if the various contingencies that have 

 been enumerated can be reduced to some common 

 factor, some progress will have been made in its dis- 

 covery. In the analogous case of beri-beri it is 

 known that the quantity of vitamin B which is re- 

 quired to avert the onset of polyneuritis in experimental 

 pigeons is proportional to the quantity of carbohydrate 

 in the diet. It seems likely that the quantity of 

 vitamin A necessary to prevent or cure rickets varies 

 similarly with the intake of other food. A full diet 

 and rapid growth encourage its onset : a meagre 

 stunting allowance is to some extent a preventive. 

 The quality of the food is evidently also of importance : 

 it must contain an adequate and balanced supply of 

 the materials necessary for bone formation, and, 

 though this is still obscure, the right kinds of proteid 

 (animal rather than vegetable) and no large excess of 

 carbohydrate. It also makes a difference whether the 

 food absorbed into the economy is used for energy 

 production or for storage and growth. Exercise, even 

 that brought about by the irritation of the itch, 

 according to Dr. John Mayo (1674), is antagonistic to 

 rickets, and if the child cannot take it in the ordinary 

 way massage and electrical stimulation may supply it. 



It appears, therefore, that the amount of vitamin 

 B which is necessary varies with the proportion or 

 quantity of food which is not used for energy production. 

 If all other conditions are as favourable as possible, 

 the vitamin may with some children be reduced 

 without ill results to amounts which appear to be very 

 small by the available method of testing on growing 

 rats : from which comes the conclusion that the vitamin 

 NO. 2752, VOL. I 10] 



has not much to do with the aetiology of rickets. If, 

 on the other hand, all or some of the other condi- 

 tions are unfavourable, the quantity of vitamin — the 

 abundance, e.g., of butter or cod-liver oil — may make 

 all the difference between a healthy and a sick child : 

 hence the conclusion that vitamin B is the most 

 important factor. Even in respect of the necessary 

 components of bone, the vitamin is quantitatively 

 important. Rickets may be induced in rats by a 

 deficiency of vitamin A and of calcium, but not by a 

 deficiency of either substance alone. The vitamin in 

 this case enables the growing tissues to make use of a 

 concentration of calcium which otherwise they would 

 be unable to utilise for bone formation. Such observa- 

 tions may in time elucidate the relative weight of 

 the various factors of which at present it is known 

 only that they are quantitatively related to one 

 another. 



To bring the influence of ultra-violet rays on the 

 skin into this conception of the causation, or rather 

 the contingency, of rickets, it is not difficult to believe 

 that it acts by increasing general metabolism, in other 

 words by giving exercise. It is known that inflamma- 

 tory and sub-inflammatory processes in the skin 

 may lead to the generation of substances which are 

 absorbed into the circulation and affect the whole 

 body, e.g. by increasing the susceptibility of the whole 

 skin to the action of some local irritant. By some 

 similar process, metabolism might easily be affected. 

 It is also possible that vitamin A is developed in the 

 skin under this form of stimulation, though thenocturnal 

 and crepuscular habits of our pigmented hairy pre- 

 decessors make it difficult to explain the phylogenetic 

 history of the mechanism. Whatever the solution, 

 the observation that rickets may be cured by short 

 exposures to the mercury vapour lamp in hospital 

 wards provides a welcome experimental confirmation 

 and partial analysis of the sociological finding that 

 the conditions of life in the dreadful tenement flats 

 of Glasgow are per se conducive to the disease. 



The question therefore "What is the causeof rickets?" 

 is at present as insoluble as the problem "Is the tubercle 

 bacillus the cause of tuberculosis ? " The answer in 

 both cases is that it depends on circumstances. In the 

 latter case we have, however, reached the stage when 

 we can say that tuberculosis is impossible without 

 the tubercle bacillus : the bacillus has been identified 

 as the ultimate limiting factor. That absence or 

 deficiency of vitamin A occupies the same position in 

 respect of rickets has yet to be shown. It seems likely 

 that it does, but the demonstration has not been made 

 that cod-liver oil will avert rickets when all other 

 germane circumstances have been arranged to 

 provoke it. 



