There is one other set of substances which require a brief notice, among those having the power of destroying the lower forms of organic life. The various substances of vegetable origin, which from their sweetness are usually ranked with sugar, though not all of them capable of undergoing the vinous fermentation, have been ascertained to possess in some degree the antizymotic property. They have been very long employed as preservative of vegetable substances against spontaneous change, especially the proper cane-sugar, both in household economy and in pharmaceutic practice. After the discovery of the extraordinary power, possessed by sugar and glycerin, of protecting against higher oxidation the protoxides of the metals, particularly of iron, it was natural to ascribe its influence in preserving fruits, etc., to a similar power. Now, as some bodies act apparently by their mere presence in promoting chemical reactions between other bodies; so it was reasonable to suppose that there might be agents, having a similar power of preventing by their presence such reactions when otherwise disposed to occur; and as the former were said to be catalytic, so the latter might be designated as anticatalytic. Such might seem to be the case with saccharine liquids in preventing fermentation. But I have no doubt that there is some positive agency yet to be discovered, besides mere presence, which enables both the catalytic and anticatalytic bodies to exercise their peculiar functions; and, in relation to the antiseptic or antizymotic powers of saccharine liquids, the nature of this agency seems to have been ascertained by Dr. Louis Mandl, of Paris, to whose very interesting investigations into this subject reference has been already made. (See Note, p. 830.) On putting aquatic animals into saccharine solutions, he found them, after a certain length of time, invariably to perish. Among these solutions he includes not only the proper sugars, capable of undergoing the vinous fermentation, as cane-sugar, glucose, lactin, etc., but others having a sweet taste, though destitute of the fermenting property, such as glycerin, glycyrrhizin, mannite, etc.; their sweetness, and chemical constitution as oxyhydro-carbons, being their distinguishing character. The fatal effect on aquatic animals he ascertained to be owing to an extraordinary osmotic power of these solutions, by which the current of movement through membrane towards them is much more vigorous than in the reverse direction. The rapidity with which death occurred he found to be proportionate to the strength of the solution, and to be influenced by the kind of saccharine matter used. in reference to the latter point, Dr. Mandl did not find the cane-sugar most powerful; on the contrary, glycerin and mannite were much more rapid in their action than the true sugars, and the sugar of milk was the slowest. All sorts of animals capable of living in water were tried; the infusoria, the molluscs, the annelides, the crustacean, the batracians, the aquatic insects, and fish, all suffered, though with greater or less rapidity. Before perishing, the infusoria underwent various changes in their movements and organization; the motions being diversified and often rapid; till at length they gradually slackened, and ceased at the moment of death; while the animalcules first contracted, afterwards dilated, and at last underwent a complete dissolution. Having examined these results, Dr. Mandl made various experiments to determine the agency by which the effect was produced, and, having satisfied himself that the death of the animal was caused neither by poisoning, alteration of the blood, fermentation, the absence of air, nor the viscosity of the liquid, he traced the cause at length to the osmotic force referred to; osmosis being defined by him to be the interchange which takes place between two liquids separated by permeable membrane; the stronger current being designated by the ordinary term of endosmosis, the feebler in the contrary direction exosmosis; and the property of the liquid which attracts in either being its osmotic power, which is greatest in the liquid the bulk of which increases at the expense of the other. The animals perish in consequence of the greater osmotic power of the saccharine liquid, towards which the endosmotic current is directed, until at length they become collapsed through the loss of their nutritive fluid. This power of sugar extends to all the lower organized beings; the vegetable as well as the animal perishing, when surrounded with saccharine solutions of the necessary strength. Thus is explained the antiseptic power of sugar; as none of the organisms which produce vegetable and animal decay can exist when in a certain degree exposed to its influence. it is true that sugar itself is the subject of fermentation, and destroyed by it; but this is because the saccharine solution is not sufficiently strong for the full exercise of its osmotic power. Hence the practical inference, that these saccharine substances, and particularly glycerin, which appears to possess the power in the highest degree, are useful as external applications to diseased surfaces, not only by their demulcent, or simple protective action, but by destroying or preventing the development of those minute beings which cause or contribute to the offensiveness of the morbid surfaces, and aggravate the disease. it is obvious that, in consequence of the possession of this power, glycerin and other liquids of the kind may be applied in various ways to the preservation of health, and to our individual comfort.

After the above remarks had been sent to the press, my attention was called to recent communications in the American Journal of Medical Sciences, which had previously escaped my observation, from which it appears that pure sugar has been very satisfactorily used as a local application in hospital gangrene. it was employed in solution by Dr. Walter F. Atlee, of Philadelphia (Jan. 1864, p. 222); and was thickly applied, in the form of powder, to gangrenous ulcers, with a view to its known influence in preventing oxidation, by Dr. John H. Packard, of the same place. (Jan. 1865, p. 117.) it is gratifying thus to find the inferences as to the use of sugar, deduced from the experiments of Dr. Mandl, justified to some extent by practical experience. it is scarcely to be doubted that the sugar acted, in these cases, by its antizymotic power; and, as glycerin possesses this in a considerably greater degree than proper sugar, it would probably have proved even more efficient.