254 Dr, E, Lankester, [May 4, 



fruit of the plant. Six layers of cellular tissue were described between 

 the albumen or perisperm of the seed, and the outside of the grain : — 

 1. Theepicarp; 2. The sarcocarp ; 3. The endocarp — (these belong 

 to the fruit ; 4. The testa of the seed ; 5. A secondary membrane ; 

 6. The covering of the perisperm. These layers constitute the bran, 

 which is separated from the fine flour. They contain the same chemi- 

 cal constituents as the flour, and, so far from being objectionable, are 

 a desirable addition to the flour. The gluten of the flour is represented 

 in the bran by a principle, called by its discoverer cerealin. Like 

 gluten, it acts as a ferment ; but its power in this respect is said to be 

 destroyed at a temperature of 150° Fahr. It is soluble in cold water, 

 and in that state acts as a ferment. Bran tea accelerates the changes 

 of fermentation. It is this agent, which during the fermentation of 

 bread gives the brown colour to meal bread. Twenty-one ounces of 

 wheat yield five ounces of bread, and sixteen ounces of fine flour. One 

 pound of flour contains 



Water ', 21 ozs. 



Gluten 2 „ 



Albumen ...... i ?> 



Starch 9J „ 



Sugar i"' „ 



Gum \ „ 



Fat 1 „ 



Cellulose i ?> 



Ashes i >} 



The gluten and albumen are flesh-forming substances, sugar and 

 starch heat-giving. In the making of fermented bread, yeast is added 

 to the flour, and the gluten is put into a state of change, but not de- 

 composed. A small portion of the starch is converted into glucose, 

 which is decomposed, and alcohol formed, and carbonic acid produced. 

 The carbonic acid gas escaping from the mass vesiculates the bread. 

 The quantity of starch changed in this process is very small. It is 

 expressed by the quantity of carbonic acid gas necessary for the vesi- 

 culation of the bread, as little or none of this gas escapes in the rising 

 of the bread. The conversion of starch into glucose during the fer- 

 mentation of the bread does not appear to be greater than is necessary 

 to form the carbonic acid for vesiculation. The starch during fer- 

 mentation acquires the power of being more quickly converted into 

 glucose and its subsequent products, than when heated and not exposed 

 to this process. This is probably the great peculiarity of fermented 

 bread, that the starch more rapidly passes into a state of change. 



When the starch of wheat has already acquired this tendency to 

 change, from the sprouting of the wheat, the flour forms a sweet, 

 heavy, and sticky bread. In order to prevent this, alum is employed. 

 Alum is not necessary to the making of palatable bread from *' sound " 

 flour, but it is necessary for the making of saleable bread from unsound 



