Page:Thruston speech upon the progress of medicine 1869.djvu/9

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Since this time many other organic substances have been made either directly from the elements or intermediately through an ascending series of alcohols and acids. Formic acid, a secretion of ants, and bodies as high in the scale as Benzole (C₆H₆), have been produced by the direct union of the elements. And many other bodies have been made indirectly—such, for instance, as Alizarine, a component of madder dye; Coumarin, the odoriferous principle of the Tonka bean; Leucine, derived from Valeral-Ammonia, also a product of animal decomposition; and it has lately been reported that Neurine, the base of protagon, a substance extracted by Liebreich from the human brain, has been formed synthetically by Wurtz.

The methods by which these bodies may be made has been reduced to a system, by the labours of Berthelot and Wurtz, Frankland and Duppa. Thus, by substituting organic radicals for certain atoms of oxygen in organic ether, fatty products, with a carbon index as high as 12 (C₁₂H₂₄O₃)^[1], have been obtained, and there is scarcely any limit to this production.

Much of this success is undoubtedly due to the modern views of the constitution of organic bodies; not only the composition, or the relative proportion of the simple elements in an organic compound, is now sought for; the mode of their grouping, their structure, is examined^[2].

1. Di-amyl-oxalic acid.
2. Protagon the crystallizable essential constituent of the brain is a good instance of this mode of investigation. Its composition as ordinarily given is C₁₁₆H₂₄₁N₄PO₂₂ but now chemists declare first that it is a combination of an acid, phospho-glyceric acid, with a base, neurine = C₅ H₁₅ O₂ N, and then neurine can be artificially prepared by acting upon trimethylamine by Ethylene Oxide. It is an ammonium in fact, with three of its atoms of hydrogen replaced by methyl, and one by ox-ethyl, in other words, that it is a hydroxide of tri-methyl-ox-ethyl-ammonium; the type is thus shown:

   K	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$O;	NH4	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$O;	N(CH3)3C2H4 (OH)	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$O = C5 H14 N(OH).
   H		H		H

   I am indebted to my friend Dr Roscoe for this example.