162 THE POPULAR SCIENCE MONTHLY. 



tinue the tissue-building process during the night. Thus the plant 

 during the day stores up sun-force sufficient to do its work during the 

 night. It has been suggested by Dr. J. C. Draper, 1 though not proved, 

 or even rendered probable, that the force of tissue-building {forceplas- 

 tique) is always derived from decomposition, or combustion of organic 

 matter. In that case, the force of organic-matter formation is derived 

 from the sun, while the force of tissue-building (which is relatively 

 small) is derived from the combustion of organic matter thus previous- 

 ly formed. 



6. Fermentation". — The plastic matters out of which vegetable 

 tissue is built, and which are formed by sunlight in the leaves, are of 

 two kinds, viz., amyloids (dextrine, sugar, starch, cellulose), and albu- 

 minoids, or protoplasm. Now, the amyloids are comparatively stable, 

 and do not spontaneously decompose ; but the albuminoids not only 

 decompose spontaneously themselves, but drag down the amyloids 

 with which they are associated into concurrent decomposition — not 

 only change themselves, but propagate a change into amyloids. Al- 

 buminoids, in various stages and kinds of decomposition, are called 

 ferments. The propagated change in amyloids is called fermentation. 

 By various kinds of ferments, amyloids are thus dragged down step 

 by step to the mineral kingdom, viz., to C0 2 and H 2 0. The accom- 

 panying table exhibits the various stages of the descent of starch, and 

 the ferments by which they are effected : a 



1. Starch J 



2. Dextrine V Diastase. 



3. Sugar ) 



4. Alcohol and CO* Yeast. 



5. Acetic acid Mother of vinegar. 



6. CO a and HO Mould. 



By appropriate means, the process of descent may be stopped on 

 any one of these planes. By far too much is, unfortunately, stopped on 

 the fourth plane. The manufacturer and chemist may determine the 

 downward change through all the planes, and the chemist has recently 

 succeeded in ascending again to No. 4 ; but the plant ascends and de- 

 scends the scale at pleasure (avoiding, however, the fourth and fifth), 

 and even passes at one step from the lowest to the highest. 



Now, it will be seen by the table that, connected with each of these 

 descensive changes, there is a peculiar ferment associated. Diastase 

 determines the change from starch to dextrine and sugar — saccharifica- 

 tion ; yeast, the change from sugar to alcohol — fermentation ; mother 

 of vinegar, the change from alcohol to acetic acid — acetification ; and a 

 peculiar mould, the change from acetic acid to CO a and water. But 



1 American Journal of Science, November, 1872. The experiments of Dr. Draper are 

 inconclusive, because they are made on seedlings, which, until their supply of organic 

 food is exhausted, are independent of sunlight. 



8 J. C. Draper, American Journal of Science, November, 1872 



