July 28, 1923] 



NA TURE 



139 



tubing was free from holes and much time was con- 

 sumed in the work of eHminating leaks. The whole 

 apparatus was^ however, completed towards the end 

 of 1922 and, as stated, was used early in January of 

 this year for the production of liquid helium. The 

 helium was compressed with an enclosed Whitehead 

 torpedo compressor, and the liquefier was found to 

 give the best results when run at a pressure of only 

 40 atmospheres. 



Before attempting to make liquid helium all parts 

 of the liquefier were cooled as low as possible with 

 liquid air, the piping being cooled by circulating 

 through it helium that had been previously cooled to 

 liquid air temperature. When this precaution was 

 taken, it was found that liquid helium could readily 

 be made with a moderate amount of liquid hydrogen 



supplied to the refrigerator surrounding the coil P4. 

 In our experiments less than 10 litres of liquid hydro- 

 gen suf^ced to produce more than a litre of liquid 

 helium. 



I wish to take this opportunity of acknowledging 

 my indebtedness to Prof. Kamerlingh Onnes of Leyden, 

 the pioneer and outstanding authority in research at 

 liquid helium temperatures. He not only assisted me 

 very materially through correspondence and con- 

 versation, but also furnished me with drawings of the 

 installation at Leyden. 



It is hoped that with the cryogenic equipment now 

 available at the University of Toronto, a series of low- 

 temperature researches will be organised shortly for 

 workers who for any reason may not find it convenient 

 to go to Leyden to carry out investigations. 



Rickets in Vienna. 



\ NUMBER of summary publications have made 

 readily available the rapid advance in our 

 knowledge of rickets in the last few years since Mellanby 

 in 1918 brought forward serious evidence implicating 

 a deficiency of fat-soluble vitamin A, and Huldschnisky 

 in 1919 showed that the bone-lesions in children could 

 be cured by ultra-violet light, and McCollum and his 

 co-workers in 1921 demonstrated that the disease could 

 be conveniently produced in rats by defective diets. 

 Last year the Medical Research Council published the 

 survey by Prof. Korenchevsky ^ of the experimental 

 aspects and Dr. J. L. Dick ^ brought out a useful book 

 on the human disease and its history. More recently 

 an admirable survey of the whole question by Prof. 

 E. A. Park ^ has appeared, and there has now been 

 added a full account of the results of the expedition 

 under Dr. Harriette Chick,* sent in 191 9 to Vienna 

 by the Lister Institute and the Medical Research 

 Council, to study deficiency diseases under the condi- 

 tions of almost experimental accuracy and precision 

 afforded by the generous hospitality of Prof. v. 

 Pirquet's Kinderklinik. 



The report shows, beyond any reasonable doubt, 

 that the incidence of rickets may be determined by 

 diet, and that vitamin A plays an important part ; 

 that it may be prevented and cured by cod-liver oil ; 

 that it may be cured by sunshine or the rays from a 

 mercury-vapour lamp, and that a diet which in summer 

 is adequate for young infants may, in winter gloom, 

 permit its development. From the practical point of 

 view, the facts provide most of what the sanitarian 

 needs : a proper supply of cod-liver oil, or its equivalent 

 in vitamin A, and of sunshine, or its equivalent in ultra- 

 violet light, will prevent rickets, and a deficiency of 

 one may be made good by a larger supply of the other. 

 What is at present unknown is how much vitamin A 

 in the more customary forms of milk and green vege- 

 tables is wanted to give the same result as teaspoonfuls 

 of the far more potent cod-liver oil. But there is no 



' Medical Research Coiincil Special Report Series, No. 71. The Aetiology 

 and PalholoKy of Rickets from an experimental point of view. Pp. 172 + 18 

 plates. (London: H.M Stationery Office, 1922.) 4s. net. 



* London : \V. Heinemann. 



* Physiological Review, vol. iii., 1923, p. 106. 



* Medical Research Council Special Report Scries, No. 77. Studies of 

 Rickets in Vienna 1919-22 (Report to the Accessory Food Factors Com- 

 mittee appointed jointly by the Medical Research Council and the Lister 

 Institute). Pp. 203 + 14 plates. (London: H.M. Stationery Office, 1923.) 

 7S, 6d, net. 



NO. 280^, VOL. 112] 



longer any excuse for there being two schools of thought 

 disputing for a hygienic and a dietetic aetiology 

 respectively : as usually happens in such controversies, 

 it turns out that both parties are right. 



In the larger matter of the circumstances which 

 condition the proper and regular growth of bone the 

 results are of great interest. Granting an adequate 

 supply of the necessary materials — and of these 

 calcium and phosphorus are the most obvious, and 

 their importance has already been examined by direct 

 experiment^ — vitamin A is necessary : with enough of 

 this, rats grow satisfactorily in the dark (Goldblatt and 

 Soames, Biochemical Journal, vol. xvii., 1923, p. 294). 

 Ultra-violet light of about 300 /x/x has much the same 

 effect, and it was at first supposed, rather naturally, 

 that it operated by causing a photo-synthesis of 

 vitamin A. But rats on a diet grossly deficient in 

 vitamin will grow normally under the influence of ultra- 

 violet light only for a time : in the end, if no vitamin A 

 is provided in the food, growth ceases, and the animals 

 go downhill. Evidently light enables the animal to 

 make the most economical use of such store of vitamin 

 as it may have in its body or of any small amounts it 

 may receive in its food : light can only partly replace 

 vitamin, and if there is abundance of vitamin, light has 

 no favourable influence on growth. In the same way 

 vitamin makes a short supply of calcium or phosphorus 

 go further, so that, while any of the three may be a 

 hmiting factor, up to a certain point of deficiency it is 

 the sum (or product) of calcium phosphate and vitamin 

 which is the effective determinant. Light per se is not 

 a limiting factor, but may become the determinant 

 under conditions of defect in the others. 



Obvious as is the effect of ultra-violet light on the 

 naked human skin, it is a little difficult to believe that 

 it can act directly on the general body surface of hairy 

 animals such as rats : " man is naked," as Richard 

 Owen remarks, " and is the only terrestrial mammal 

 in that predicament." It is^ therefore, satisfactor}^ to 

 find it shown that air irradiated by the mercury vapour 

 lamp is effective in promoting growth in rats, as Kestner 

 showed it was in hastening the regeneration of blood 

 lost by haemorrhage : such air, in the absence of ultra- 

 violet light itself, will also cure rickets in children. It 

 does not seem to be known as yet whether radiation 

 of the body surface with exclusion of radiated air 



