MEDICINE 237 



Kinderklinic, discovered that the action of cod-liver oil on 

 the bone lesions of rickets has an exact parallel in that of 

 light. Not only so, but she was able to show that the im- 

 portant light element in this respect is the violet end of the 

 spectrum. 



This discovery led to the use of the mercury vapour quartz 

 lamp instead of sunlight. It was found that this was capable 

 of producing effects similar to the actinic solar rays and also 

 to cod-liver oil. 



It is notorious that cod-liver oil is rich in A Vitamin. 

 Thus the question at once arises whether or not sunlight and 

 other lights rich in violet rays are capable of producing A 

 Vitamin by their action on the human skin, whether in short 

 sunlight is not a food in a material sense of that term. 



In any case Dr. Chick has used the expression photo- 

 synthesis to describe the phenomenon observed by her. She 

 states in a communication on the subject to The Lancet that 

 this is " an idea which is quite new to animal physiology." 



It is interesting to apply this discovery to the known 

 habits of mankind. Thus, in northern latitudes, where sun- 

 light is a relatively infrequent meteorological condition, the 

 intake of animal fats and oils by the inhabitants is large. 

 Near the tropics, on the other hand, animal fats are but lightly 

 partaken of. One might crystallise that into the phrase ; 

 " More light less fat." 



Interesting, too, is the relation of the discovery to rickets 

 itself. This abounds in towns such as Glasgow where the 

 atmosphere is constantly charged with smoke and where, in 

 consequence, the violet rays of the spectrum are excluded. 

 It is much less frequent in sunny, open towns where there is 

 a full supply of direct, unfiltered sunlight. 



Dr. Chick suggests that the fact that rickets is not common 

 in Greenland may be explained by the large consumption of 

 cod-hver oil and other fish oils in that country by mothers 

 and children. 



In this connection the annual report of the Imperial Cancer 

 Research Fund for 1921 raises some interesting new points. 

 An attempt was made by one of the workers to test the effect 

 of a lack of Vitamin A in the diet of animals. It was found 

 that there resulted a definite diminution in the number of 

 blood platelets, and that this diminution was accompanied by 

 a susceptibihty to the attacks of organisms normally not 

 possessed of pathogenic power. 



This condition exactly corresponded to that seen in X-ray 

 and radium workers subjected to over-exposure. In other 

 words, X-rays and radium would appear to occasion the same 



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