260 SECTIONAL ADDRESSES 
formed by the liver from the pigment carotene ; this pigment occurs in 
carrots, green leaves, and various vegetables ; it is a hydrocarbon, CyyH,g, 
which is synthesised in plants by the action of light. Carotene has a 
deep colour, but Vitamin A is colourless. How carotene is converted into 
Vitamin A in the tissues is uncertain. The empirical formula C,)H3,O 
(or Cy9Hs,0) has been suggested, and it appears probable that within 
the next few years the constitution of this vitamin will be known and then 
its preparation by synthetical methods will be a possibility. 
Vitamin B—Much work has already been carried out on the various 
members of the Vitamin B complex, but the position is still obscure and 
rather confusing. It is still uncertain how many active substances are 
present and there is still no general agreement as to their properties. 
B, and B, are the only two about which definite conclusions are at present 
available. B, has been obtained in the crystalline state and contains both 
nitrogen and sulphur. The provisional formula C,,H,,ON,S has been 
suggested. It is anticipated that the pure product will be available in 
the near future. While aconsiderable amount of work has been carried out 
as to the chemical nature of Bg, little definite information has yet been 
obtained. 
Vitamin C.—The striking investigations of Szent-Gyorgyi and of 
Waugh and King have led to a great advance in our knowledge of this 
vitamin. What appears to be the essential substance in the vitamin was 
isolated and found to have the formula C,H,O, ; it was named hexuronic 
acid. ‘The preparation of a larger quantity of the material from the 
juice of Hungarian red pepper by Szent-Gyorgyi has enabled the consti- 
tution of the acid to be worked out by Hirst, Cox and Reynolds at 
Birmingham. ‘The substance is now named ascorbic acid, and its anti- 
scorbutic properties are so marked that it may well prove to be Vitamin C 
itself. 
Vitamin D is now available as a commercial preparation under the 
name ‘ Calciferol.’ It is prepared by the irradiation of ergosterol with 
ultra-violet light ; its formula is C,,H,.O. 
The discovery of vitamins has undoubtedly thrown much light on many 
_ of the difficult problems of nutrition and disease, and there can be no 
doubt that, as our knowledge of these substances increases, more and 
more use will be made of them in feeding. Already some notable advances 
have been made. The close connection between the yellow coloured 
pigment carotene and Vitamin A has just been referred to. Milk and 
butter produced in the summer months, when the cows are at pasture, 
have a yellow colour which is associated with the presence of carotene and 
of Vitamin A. On the other hand, butter produced from winter milk, 
when the cows are stall fed, is much whiter in colour and has a much 
lower content of carotene and Vitamin A. ‘The popular view which 
associates the yellow colour of milk with ‘ richness’ is therefore not at 
fault, and incidentally the importance of prohibiting the colouring of 
butter and cheese should be mentioned. ‘The problem was how to 
provide food with the necessary carotene or Vitamin A content during the 
winter months. Experiments on the artificial drying of grass carried out 
at the Agricultural Research Station at Jealotts Hill, Berkshire, have 
