Dr Anderson on the Properties of Picoline. 147 



results of unexpected interest and importance. These re- 

 sults have affected, in no inconsiderable degree, the recent 

 progress of the science ; and their influence has been of a 

 twofold character, both general and particular, exerted in 

 the former case in the development of some of the more re- 

 markable general doctrines of organic chemistry ; in the lat- 

 ter, in the important light thrown by their investigation on 

 the constitution of the substances from which they are de- 

 rived, and the facilities they have afforded of following out 

 connections, which the examination of the original substance 

 either does not at all present to our view, or, at least, indi- 

 cates only in an imperfect or dubious manner. Added to 

 to this, we have the remarkable fact of the appearance among 

 these products of substances in some cases identical with 

 those occurring in organised beings ; and in others, present- 

 ing analogies of the very closest character with the actual 

 products of vital affinity, which, taken together, afford abun- 

 dant reason for pursuing the investigation of substances 

 which have already afforded results of so remarkable a cha- 

 racter. 



Setting aside altogether those substances, the occurrence 

 of which is so frequent, that they may be called the general 

 products of destructive distillation, such as carbonic acid, 

 light carburetted hydrogen, olefiant gas, acetic acid, &c., 

 it may be laid down as a general rule, that each individual 

 compound produced during such a process, is formed by the 

 destruction of a limited number of substances only, which 

 bear to each other, and to the product, a more or less inti- 

 mate connection in constitution or chemical relations. In 

 those instances in which we have been enabled to submit to 

 destructive distillation substances of a definite and simple 

 constitution, in a state of chemical purity, and Vhere an uni- 

 form temperature has been preserved, the results have been, 

 for the most part, of an exceedingly simple and intelligible 

 character ; but in proportion as the atom becomes more com- 

 plex, so also do the products of its decomposition, and the 

 explanation of the results is found to be proportionately dif- 

 ficult and unceii^ain. These difficulties and uncertainties are 

 increased in a still higher degree, in the case of a substance 



