PHYSIOLOGY 



unless the oxygen of the air is excluded. Dr 

 Zilva, of the Lister Institute, has compared the 

 anti-rachitic value of the crude oil and of these 

 so-called ' refined ' products, and found that the 

 potency of the latter is reduced many hundred- 

 fold as compared with the natural oil. Dr Drum- 

 mond has now in his laboratory a crude fish-liver 

 oil of which a single drop per diem is able to accom- 

 plish the work of Hopkins' teaspoonful of milk. 

 A drop of this oil, remember, is not a drop of pure 

 vitamin, though if it were the result would be mar- 

 vellous enough. It is a drop of oil, and when one 

 deducts from its weight the amount of the known 

 substances in it, which can be estimated (the actual 

 oil or fat, etc.), what remains ? Merely an in- 

 finitesimal quantity. Could one go further as an 

 illustration of the overwhelming importance of the 

 infinitely little ? 



There are many other chemical substances that 

 have been separated out from the different parts 

 of the body which, in a high degree of attenua- 

 tion, will produce marked results. One of them 

 I should like further to allude to, because it has 

 brought into prominence, or was itself brought into 

 prominence, by a study of what Harvey discovered, 

 the circulation of the blood. I must take for 

 granted that, although the majority of my readers 

 are not physiologists, they at least do know that 

 blood goes round and round in the body. The 



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