In order to find a method of preserving bodies, and animal matters in general, it was essential to examine the action of chemical substances to which may be attributed properties which produce upon the constituent parts of these matters an immediate action; it is necessary also, that they should be easily procured, and that they be of a moderate price. I am satisfied that acids do not preserve animal matters; they disorganize them more or less promptly, in direct proportion to their concentration. Many weak acids, among others hydrochloric acid, at five degrees, may be employed to dissolve the calcareous salts from the bones; nitric acid also, at five degrees, may be brought into use in some particular cases; for example, when it is wished to study the nervous system; but then the bones are softened, the geline is in part disorganized, the muscles are discolored, and become flabby, as well as the viscera; the nerves only remain of a pearly blue, strongly pronounced. Arsenic acid has a very marked action on animal matters; I shall make it known without delay in my second memoir upon gelatine. It preserves bodies well, but appears to favour their desiccation. In the details of experiments made under the surveillance of the commissioners of the two academies, I shall cite the effects produced by the employment of this substance. Acetic acid preserves flesh only by drying it. This acid weakened, or vinegar, retards putrefaction, softens the bones, as well as the muscles, which are discolored by its action. Concentrated lies dissolve all animal matters; weak alkaline solutions disorganize more or less promptly the same substances. A very small quantity of alkali suffices, when warm, to decompose very large masses of glue. This effect is often produced through ignorance in the manufacture of strong glue. Salts only preserve meats when employed dry, or in very concentrated solutions; it is necessary that their affinity should be sufficiently great to absorb all the water of combination of animal matters. It may be then affirmed that salt only preserves meat by drying it; thus those salts more soluble in warm than in cold water; may, when injected warm, in a saturated solution, be considered as a good means of preservation, but which cannot be employed for anatomical purposes, because of the crystals which form in the organs during the cooling of the injected liquor. Salts with a metallic oxide base have in general little affinity for geline, and do not preserve well; those which are poisonous being alone excepted. The salts of copper, and above all those of mercury hinder putrefaction; but many causes are opposed to their employment. 1. Their action is not sufficiently energetic to give them the preference: 2. They are always dangerous when employed in large quantities. 3. They are very injurious to dissecting instruments. 4. In fine they are too costly.