O' Brien — The Proteids of Wheat. 21 1 
acids. The precipitate which we obtain by water resembles 
gluten ; that obtained by means of ether resembles the residue 
on evaporation. No attempt to isolate the mother-substance 
by any other means has been successful. Dilute potash and 
hydrochloric acid alike remove it, but this is necessarily in the 
derived form of an alkali-albuminate or acid-albumin. 
Therefore of the proteids as they exist in wheat we can as 
yet affirm nothing definitely : but we must now add to those 
already described as extracted (namely, myosin and proteose) ; 
another globulin, vitellin ; and a fourth which readily passes 
into the hydrated state, the mother-substance of gluten- 
homologous with the zein of maize and Osborne’s alcohol- 
soluble proteid of oats, in its solubility in alcohol, but dis- 
tinguished from them by its physical properties dependent 
on its capacity for hydration. 
III. 
The endosperm of wheat comprises not only the central 
starch-containing cells which constitute the greater part of 
flour, but a peripheral layer of cells, rich in oil and containing 
numerous small aleuron-grains. The contents of these cells 
have long been known to be very rich in nitrogen, causing the 
percentage of nitrogen in bran to far exceed that in flour. 
An account of the proteids of wheat must therefore include 
some descriptions of the aleuron-cells and their contents. 
There is no necessity to refer to the general literature of 
the subject of aleuron-grains : references to the earlier part 
are given fully by Pfeffer 5 , and are brought down to a recent 
date by Liidtke 12 . I need therefore only mention what has 
special reference to the aleuron-grains of the Gramineae. 
Maschke 3 (1859) recognised them and their localisation in 
the outer layers of rye, but gave no special account of them. 
Sachs 4 (1862) described the outer endosperm-layer of wheat 
as being rich in nitrogenous substances and containing oil. 
Pfeffer 5 gave some attention to them in his work on 
proteid-grains (1872), but it is somewhat difficult to know 
whether his remarks actually refer to what we now know 
