1883.] NATURAL SCIENCES OF PHILADELPHIA. 309 



drops of ether have been added to prevent germination, they will, 

 in a few days, become thoroughly softened, and the contents of 

 such a grain may then be squeezed out as a white tenacious mass. 

 Examination of the remaining bran shows the "gluten-cells" 

 undisturbed, closely adhering to the cortical protective layers. 

 By now carefully washing the white extruded mass, the major 

 part of its starch may be removed ; and upon the addition of a 

 drop of iodine solution, microscopic examination shows numer- 

 ous networks of fine yellow fibrils, still holding entangled in their 

 meshes many starch granules colored blue by the iodine. In 

 carefully washed specimens, these sponge-like networks are seen 

 to retain the outline of the central starch-filled cells, and evidentl}' 

 constitute the protoplasmic matrix in which the starch granules 

 lay. Upon gently teasing such a specimen under a moderate 

 amplification the fibrils will be seen to become longer and thinner 

 in a manner possible only to viscid and tenacious substances — a 

 class represented in wheat b}' gluten alone. 



An eminently satisfactory proof of the proteid nature of these 

 central networks ma}- be obtained by heating the specimen in the 

 solution of acid nitrate of mercury (Millon's reagent), when the 

 fibrils will assume the bright pink tint characteristic of albumen- 

 oids under this treatment. The results of the application of the 

 xanthoproteic and biuret reactions are equally conclusive, but more 

 care is required in the use of these proteid tests, and the resultant 

 differentiation is not so clear. Reticuli similar to those above 

 described, but much broken and smaller, ma}" be seen, upon close 

 examination, scattered throughout fine white flour, without the 

 addition of any reagent. 



By general consent, the albumenoids of the wheat grain are 

 grouped together as gluten, which is, however, further separable 

 into gluten-fibrin, gliadin and mucedin, proteid bodies practically 

 equal in nutritive value, but differing in certain physical proper- 

 ties, notably that of solubility. It must, therefore, be borne in 

 mind that in this, as in all other methods of separating gluten 

 from the other constituents of the gi ain, its relatively small soluble 

 portion is removed with the starch, and that any estimate of the 

 quantity of gluten based upon such methods will probably be 

 rather under than over the actual amount. 



2. In even the thinnest sections of the wheat grain, the gluten 

 of the central portion is always masked by large numbers of starch 



