60 HYDROCARBONACEOUS PROXIMATE PRINCIPLES. 



juices, the starch previously stored up being at some period of growth 

 changed into sugar by the molecular actions going on in the vegetable 

 fabric. Finally, various nitrogenous animal substances produce the 

 same effect. The contact of human saliva or the intestinal juices at a 

 temperature of 37.5 (10(P F.) rapidly transforms hydrated starch into 

 sugar. 



A special interest attaches to starch from the fact that it is the first 

 organic substance produced, in the process of vegetation, from inor- 

 ganic materials. The animal body is incapable of forming organic 

 matter, and must therefore be supplied with these substances in the 

 food. But vegetables have the power of combining inorganic ele- 

 ments in such a way as to produce a new class of bodies, peculiar to 

 the organic world, and capable of serving for the nutrition of animals. 

 This is shown by numerous experiments, in which seeds or young 

 plants, artificially cultivated in a soil of clean sand, and moistened only 

 with solutions of various mineral salts, 1 have germinated, grown, and 

 fructified, increasing, many times over, the quantity of organic material 

 which they contained at the beginning. 



This production of organic matter takes place in the green tissues, 

 principally in the leaves, of growing plants, under the influence of 

 the solar light ; and the first substance which makes its appearance 

 under these conditions is nearly always starch. It is produced from 

 two inorganic matters absorbed from without, namely, carbonic acid 

 and water, which are deoxidized by the green vegetable tissues, their 

 elements being re-combined, to form a carbo-hydrate. This is proved 

 by the fact that oxygen is exhaled, during the vegetative process, in 

 the same or nearly the same proportion as that in which it existed 

 originally in the carbonic acid ; and the new substance produced con- 

 tains hydrogen and oxygen in the relative proportions to form water. 

 The production of starch in growing vegetables is therefore repre- 

 sented by the following formula : 



Carbonic acid. Water. Starch. 



(C 6 12 + H 10 5 ) - 12 = C C H 10 5 . 



The starch thus formed in the leaves of plants is afterward trans- 

 formed into other vegetable substances belonging to the group of the 

 carbo-hydrates, such as dextrine, sugar, and cellulose, and used for the 

 further nutrition of the plant. When abundantly deposited in special 

 organs, such as the starchy seeds of wheat or Indian corn, or the tubers 

 of the potato, it constitutes a reserve material of nutrition, to be after- 

 ward dissolved and employed for the purposes of germination and 

 growth. It is from such natural deposits of reserve, in the vegetable 

 fabric, that starch is obtained in quantity to serve as food for animals 

 or man. 



1 Mayer, Lehrbuch der Agrikultur-Chemie. Heidelberg, 1871, Band i. 

 p. 10. 



