A frog’s heart under the influence of any poison may be finally divided into pieces so as to ascertain if any parts still contract; the significance of this is, that the particular ganglion supplying that portion of the heart has not been affected: the chief ganglia to be looked for are Remak’s, on the boundary of the sinus and auricle; Ludwig’s, on the auricle and the septum of the auricle; Bidder’s, on the atrioventricular border, especially in the valves; and Dogiel’s ganglion, between the muscular fibres. According to Dogiel, poisons acting like muscarine affect every portion of the heart, and atropine restores the contractile power of every portion. VI.--General Method of Procedure in Searching for Poison. § 31. Mineral substances, or liquids containing only inorganic matters, can cause no possible difficulty to any one who is practised in analytical investigation; but the substances which exercise the skill of the expert are organic fluids or solids. The first thing to be done is to note accurately the manner in which the samples have been packed, whether the seals have been tampered with, whether the vessels or wrappers themselves are likely to have contaminated the articles sent; and then to make a very careful observation of the appearance, smell, colour, and reaction of the matters, not forgetting to take the weight, if solid--the volume, if liquid. All these are obvious precautions, requiring no particular directions. If the object of research is the stomach and its contents, the contents should be carefully transferred to a tall conical glass; the organ cut open, spread out on a sheet of glass, and examined minutely by a lens, picking out any suspicious-looking substance for closer observation. The mucous membrane should now be well cleansed by the aid of a wash-bottle, and if there is any necessity for destroying the stomach, it may be essential in important cases to have it photographed. The washings having been added to the contents of the stomach, the sediment is separated and submitted to inspection, for it must be remembered that, irrespective of the discovery of poison, a knowledge of the nature of the food last eaten by the deceased may be of extreme value.