30 BIOLOGICAL PROBLEMS 



that matter, by the public, as of the finest quality 

 contain relatively but a small proportion of the whole 

 grain. "Patents' flour, for instance, contains only 

 about 36 per cent. The so-called "straight-grade 

 flour", a mixture of the finer qualities with "seconds", 

 represents, as already stated, about 70 per cent of the 

 grain, this being the largest proportion which usually 

 went into a white loaf before the war. The old stone 

 mills on the other hand used to yield a flour contain- 

 ing 80 per cent, and the flours used for our war bread 

 have contained from 80 up to 90 per cent of the whole 

 wheat. 



When the miller increases the degree of "extrac- 

 tion " to use the technical expression it means, of 

 course, that a greater relative amount of those parts 

 of the grain which lie nearest to the husk go into the 

 flour. The chemical and physical characters of these 

 parts are somewhat different from those of the inner 

 part, the white endosperm of the kernel, which was 

 found alone in the really white loaf. Another con- 

 stituent of the grain which has characters of its own 

 is the germ or embryo the representative of the 

 future young plant. It is somewhat difficult to trace 

 the exact fate of this during the process of milling. 

 It is safe to say, however, that, while the modern 

 process practically eliminates it from the flour, the 

 stone mill left in a considerable proportion, while 

 a flour containing 90 per cent of the grain will, how- 

 ever milled, contain nearly the whole of it. 



It is clear that the real point at issue in the con- 

 troversy concerning the relative merits of white and 

 brown bread is the actual nutritive value of these 

 special parts of the wheat berry which are absent from 

 the one bread and present in the other. Before con- 

 sidering this important question further, it will be 

 well to deal briefly with a point which, though of 



