5 0* 



Gerhard? s Organic Chemistry. 95 



We cannot retrace this process and bringing together the formic 

 acid, carbonic acid and water, by a process of dexoydation re- 

 produce the sugar. These products were formed by a combus- 

 tion in which a part of the carbon and hydrogen is converted 

 into carbonic acid and water, and the power of reducing them 

 belongs to the vegetable organism, where the chemical affini- 

 ties are controlled and directed in a peculiar way by the vital 

 force. It is thus that in these operations, we commence with 

 a complex body and by a process in which its carbon and hy- 

 drogen are gradually oxydized, reduce it to simpler and simpler 

 forms. 



There are however some exceptions to this law ; a few syn- 

 thetical processes are known by which we can unite the ele- 

 ments of simpler compounds to form one more complex. Two 

 polymeric bodies are known which are formed by a grouping to- 

 gether of several molecules of aldehyde ; and many of the essen- 

 tial oils undergo a similar change by action of sulphuric acid. 

 The decomposition of organic substances by heat offers some re- 

 markable instances of this kind ; in the dry distillation of wax 

 ^ 1 9H3 % 0, we obtain paraffine, which is C 2 4 H^ m 



In view of these relations, observes our author, " we may con- 

 sider all organic substances as the result of the combustion of 

 others more rich in carbon and hydrogen, or reciprocally as the 

 products of the reduction or complication of other bodies contain- 

 ing less carbon and hydrogen. 5 ' 



" In considering from this point of view the whole of organic 

 substances, we observe that they offer successive and almost in- 

 sensible gradations, in such a manner as to form an immense 

 scale, the two extremities of which are occupied, the one at the 

 summit, by the cerebral substance, albumen, fibrine and other 

 bodies still more complex ; and on the other at the bottom by 

 carbonic acid, water and ammonia, preceded by wood-spirit with 

 formic acid and the other bodies derived from it." 



u The chemist in applying the agents of combustion to sub- 

 stances, descends the scale, that is to say, he gradually simplifies 

 these substances by burning successively, portions of their car- 

 bon and hydrogen. On the contrary, he remounts the scale in ap- 

 plying to organic substances the processes of reduction. These 

 considerations conduct us to an exact appreciation of the princi- 

 P es upon which we may classify all organic substances in a sim- 

 ple and complete manner, which does not have recourse to hy- 

 pothesis, but confines itself strictly to the limits of experience. 77 

 PP- 21, 22. 



In the examination of organic substances, we observe that 

 those which correspond in their chemical characteristics, present 

 a similarity of relation in the proportions of their constituent 

 foments. The alcohols, embracing wood-spirit, spirit of wine, 



