The _hydro-cyanic acid_ has been discovered, in a state of perfect formation, in a variety of vegetables, whose peculiar odour at once announces its presence; such are bitter almonds; the kernels of apricots, cherries, particularly the _Cerasa Juliana_, and several plums; the leaves of laurel; and peach blossoms; and the bark of the _prunus padus_, or bird-cherry tree. The only mineral substance, in which hydro-cyanic has yet been detected is the _Fer Azuré_ of Hauy.[437] Animal substances, although they do not contain it ready formed, yet, when treated with an alkali at a high temperature, they yield it in great abundance, in consequence of the combination of its elements. _Action of hydro-cyanic Acid as a Poison._ The experiments which have been instituted with a view to ascertain the exact effects of this substance upon animal life, very clearly prove that the acid of _Gay-Lussac_ is one of the most active poisons in nature; and that the various vegetable bodies, into whose composition it enters, exert an energy, corresponding with the quantity of this constituent, and the degree of concentration, in which it exists. The experiments of _M. Orfila_ were made with Prussic acid, prepared according to the process of _Scheele_, and consequently containing a great proportion of water, as we have already explained; and yet the effects which followed its administration were extremely energetic. From the _Annales de Chimie_, for October 1814, we learn that a professor of chemistry, having inadvertently left on his table a phial filled with a solution of Prussic acid in alcohol, a female servant, who had been seduced by its agreeable smell, drank a small glass-full of it, and fell dead at the end of a few minutes, as if struck by apoplexy.