ILLUSTRATION FROM THE MAKING OF BREAB. 79 



ical processes. Their origin is lost in a remote antiquity, and so uni- 

 versally are their benefits acknowledged that their use is diffused all over 

 the world. 



Experience proves that the best bread is made from fine wheaten flour, 

 mixed into a paste with a due proportion of water. A certain quantity 

 of a nitrogenized substance undergoing incipient oxidation, termed yeast, 

 is added, and the whole submitted to a gentle temperature. All flour 

 contains a small quantity of sugar ; on this the yeast immediately acts, 

 dividing it, as in the former case, into carbonic acid and alcohol. If 

 enough sugar is not present, more under the circumstances is formed from 

 starch. The acid gas, as it is set free, can not extricate itself from the 

 surrounding dough, but expands into a thousand little vesicles or bub- 

 bles, which give that peculiar porosity for which this kind of bread is so 

 highly prized. At this period, before baking, the other substance which 

 has arisen from the destruction of the sugar the alcohol is contained 

 in the dough, and is expelled therefrom along with the excess of water 

 by the high temperature of the oven, which also, by increasing the expan- 

 sion of the included gas, adds to the porosity of the bread. In some 

 baking establishments arrangements have occasionally been made to con- 

 dense the alcohol as it rises from the bread. The good and evil of life 

 are often closely intermixed. The advocate of total abstinence from al- 

 cohol may with reason look upon half-baked bread distrustfully. The 

 enemy is lying in ambush for him. 



On some occasions, instead of using yeast, a piece of leaven, that is, 

 dough in a state of incipient putrefaction, is employed. The mode of 

 action is, however, the same. The use of this material well illustrates 

 the progressive nature of these changes, and how the action gradually 

 passes from point to point of the entire mass. It is written, "A little 

 leaven leaveneth the whole lump." 



In the cases here presented the action is one of subdivision. A com- 

 plex atom has its constitution broken up, and is separated These actions, 

 into distinct parts. When such a change is once commenced ^^^are dl ~ 

 in a mass, there is a liability for the whole to become in- subdivisions, 

 volved, just as, when we ignite one point in a pile of combustibles, the 

 fire spreads throughout ; or as, when on one part of a piece of fresh meat 

 a small portion in a putrescent state is laid, the corruption, with measured 

 rapidity, proceeds from part to part, until the whole is decayed. One 

 after another, the particles submit in succession. 



Over all these subdividing actions heat exerts the most extraordinary 

 influence, so that for a given effect to be produced it is abso- influence of 

 lutely necessary that a given temperature should be main- gubdMSng 686 

 tained. Thus, if we take the saccharine juice of almost any actions, 

 kind of fruit, and cause it to be acted on by a changing nitrogenized body, 



