424 . CHEMICAL COMPOUNDS. PART n. 



at once one of the most valuable, contradictory and 

 powerful agents in nature. 



Chemists have formed by synthesis compounds identi- 

 cal with all the fixed and essential oils, for confectioners 

 can now give the flavour of the pear, orange, quince, 

 pine apple and other fruits by means of artificial chemi- 

 cal compounds. All the saccharine substances have not 

 yet been artificially obtained, nor the albuminous sub- 

 stances, albumen, fibrin, and casein. 



It cannot be a matter of surprise, when chemists form 

 organic substances out of inorganic elements, that they 

 should succeed in transforming compounds produced by 

 living plants into new compounds, as that of changing 

 the vegetable acids into alcohols, which is now done. 

 But some of the acids themselves are synthetically formed 

 out of inorganic elements ; as for example the oxalic, the 

 most common of all the vegetable acids, which is found 

 most abundantly in the Oxalis or wood sorrel, and is a' 

 frequent constituent of the highest and lowest plants. 

 The formic acid, which is the acrid stinging principle in 

 ants, is also synthetically formed ; it is found in the juice 

 of the stinging nettle and in decaying pine leaves, 

 and contains hydrogen like all the other vegetable acids. 

 These acids result from an augmentation of oxygen 

 during nocturnal respiration, which penetrates deeply 

 into the vegetable structure. 



Octahedral, prismatic, and stellar microscopic crystals 

 formed by the chemical combination of the natural acids 

 with bases imbibed by the roots, are deposited in the 

 cells under the skin, and in all parts of plants. However, 

 they appear most frequently as bundles of needle-shaped 

 crystals of carbonate of lime, lying side by side in the 

 hollow of a cell. They are known as raphides, from 

 raphis a needle, and may be easily seen under the skin 

 of the medicinal squill. Large single crystals of oxalate 

 of lime, octahedral or prismatic, are found in the cells 

 under the skin of the onion and other plants ; and stellar 



