50 THE BUTYRIC ACID GROUP. 



acids by its volatility, and from other acids of this group by its 

 power of reducing the oxides of mercury and of silver ; but it must 

 be recollected that if we obtain formic acid by the distillation of a 

 mixture with sulphuric acid, this formic acid may have been pro- 

 duced by the action of the sulphuric acid on organic matter, or on 

 already formed hydrocyanic acid. We may separate it from the 

 other acids of this group by fractional distillation, since the boiling 

 point of this acid is lower than that of all other homologous acids. 



Physiological Relations. 



Occurrence. Formic acid has hitherto been much more fre- 

 quently found as a product of the decomposition of many organic 

 substances, as for instance in the gradual decay (Eremacausis) of 

 coal, than as an educt of the animal body. It has only as yet been 

 positively proved to exist pre-formed in ants (especially Formica 

 rufa) ; Bouchardat and Sandras* believe, however, that they have 

 found it in the blood of dogs which for a long time had been fed 

 with sugar. According to Scherer,t there are contained in the 

 juice of flesh not only lactic, inosinic, and phosphoric acids, but 

 also formic, acetic, and several other acids of this group. 



[Will of Erlangen has recently shown that the active poisonous 

 principle in certain caterpillars is formic acid. It exists in a free, 

 concentrated state in all parts of the animal, particularly in the 

 faeces, in the greenish-yellow matter that exudes when the animal 

 is cut, and in the hollow bristles. G. E. D.] 



Origin. Notwithstanding that the principal processes in the 

 animal organism are based on an oxidation, and that, on the other 

 hand, in the artificial oxidations of animal substances, formic acid 

 is produced, we do but rarely meet with this acid in the animal 

 kingdom : indeed, even with reference to the ants, it is by no means 

 certain that they actually produce formic acid, for we know that 

 juniper berries and the cones of several kinds of pine contain formic 

 acid, and that these substances are much sought after by ants. We 

 must leave this question unanswered, since it is only by direct 

 experiments that we can determine whether ants take up exactly 

 the same amount of acid as they yield. 



Bouchardat and Sandras are of opinion that the lactic acid 

 formed from starch and sugar in the blood is first decomposed into 

 formic acid before its elements are finally reduced to water and 

 carbonic acid. 



* Compt. rend. T. 20, pp. 1026 et 1085. 

 t Ann. d. Ch. u. Pharm. Bd. 69, S. 196-201. 



