Scientific Lectures. 113 



as miicli pliosplioric acid as is found in an equal weight of fine flour. 

 Let us see why this should be so. 



If you cut a grain of wheat in halves, at right-angles to its length, 

 and expqse the fresh surface to the action of a solution of a salt of 

 copper as amnionio-sulphate of copper, after a few hours you will 

 observe that a narrow belt very near the outside of the section 

 exposed by the knife has become green. This green is due to the 

 formation Qi phosphate of copper. Within this belt or circlet of beads 

 the color will liave been very slightly changed; the phosphoric acid 

 and the gluten of which it is a part, are confined to this layer near 

 the envelope. If j^ou moisten plump grains of wheat and rub them 

 between the folds of a coarse towel, you will, in a little time, sepa- 

 rate from each berry a thin, straw-like envelope, which contains little 

 or no nutritive material. This is the outer, true bran. If you 

 examine the layer next beneath, you will find it composed of tubular 

 bundles, laid side by side like cigars spread out on a table. It lias 

 been called the cigar coat, and is the inner, true bran. JSText within 

 is a delicate gauze-like coat, not continuous, and very thin ; and 

 beyond is a layer smooth on tlie outside, but filled on the inside with 

 cells, that suggest a honey comb, a single layer of cells in thickness. 

 These cells are occupied, each with a little sack containing gluten, 

 and constitute the gluten coat, seen as a row of beads in the section 

 just described. Beyond the gluten coat to the heart of the grain is 

 a mass of starch granules, supported in an open texture of cellular 

 tissue. These diagrams will illustrate the succession of coats. (Dia- 

 grani B and 0, and explanation.) 



Here is a diagram of a section of miller's bran, more magnified, 

 and another made at right angles to the first, in which you have the 

 cigar tubes opened by the slicing of the knife. (Diagram D and E, 

 and explanation.) 



If you expose the cross section of the berry to the action of a solu- 

 tion of iodine, you will find that all within the row of beads of 

 gluten will become blue. This is the characteristic reaction of starch. 

 The gluten you have noticed is confined to the enveloj)e of the 

 grain, and you will see at once why, in grinding and bolting, the 

 adhesion of the gluten layer to the outer coats of bran proper should 

 cause it to be separated from the fine flour in bolting. But a small 

 proportion of the phosphatic ingredients is found in the starch, so that 

 most of the gluten which the fine flour contains is due to the partial 



[Inst.] 8 



