Various - Chambers's Edinburgh Journal, No. 460

The many-headed public look out for 'nine days' wonders,' and speedily allow one wonder to obliterate the remembrance of that which preceded it. So it is with all newspaper topics, and so it has been in respect to the preserved-meat question. We all know how great was the excitement at the commencement of the present year on this matter. Ships' accounts overhauled; arctic stores re-examined; canisters opened and rejected; contracts inquired into; statements and counter-statements published; questionings of Admiralty officials in the two Houses of Parliament; reports published by committees; recommendations offered for future guidance; descriptions of the preserving processes at different establishments: all went the round of the newspapers, and then the topic was forgotten. It deserves to be held in remembrance, however, for the subject-matter is really important and valuable, in respect not only to the stores for shipping, but to the provisioning of large or small bodies of men under various exceptional circumstances.

A few of the simple laws of organic chemistry suffice to account for the speedy decay of dead animal substances, and for the methods whereby this decay is retarded or prevented. In organised substances, the chemical atoms combine in a very complex but unstable way; several such atoms group together to form a proximate principle, such as gluten, albumen, fibrin, &c.; and several of these combine to form a complete organic substance. The chemical rank-and-file, so to speak, form a battalion, and two or more battalions form the chemical army. But it is a law in chemistry, that the more complex a substance becomes, the less stable is its constitution, or the sooner is it affected by disturbing influences. Hence organic substances are more readily decomposed than inorganic. How striking, for instance, are the changes easily wrought in a few grains of barley! They contain a kind of starch or fecula; this starch, in the process of malting, becomes converted into a kind of sugar; and from this malt-sugar or transformed starch, may be obtained ale or beer, gin or whisky, and vinegar, by various processes of fermenting and distilling. The complex substance breaks up through very slight causes, and the simple elements readjust themselves into new groupings. The same occurs in animal as in vegetable substances, but still more rapidly, as the former are more intricate in composition than the latter, and are held together by a weaker tie.

What the 'vital principle' may be, neither chemists nor physiologists can tell us with any great degree of clearness; but it is this vital principle, whatever it may be, which prevents decay in a living organic substance, however complex. When life departs, the onslaught begins; the defender has been removed, and a number of assailants make their appearance. Air , heat , and moisture are the principal of these; they attack the dead organism, and gradually convert it into wholly different and inorganic compounds, such as water, carbonic acid, ammonia, phosphuretted hydrogen, and many others. What, then, would result if these disturbers could be warded off, one or all? It is now pretty well ascertained, that if any one of the three—air, heat, moisture—be absent, the decay is either greatly retarded or indefinitely postponed; and we shall find that in all antiseptic or preserving processes, the fundamental principle has simply such an object in view.

Sometimes the operation of natural causes leads to the preservation of dead animal substances for a great length of time, by excluding one out of the above three disturbing influences. If heat be so deficient that the animal juices become wholly frozen up, the substance is almost proof against decay. Thus, about seventy years ago, a huge animal was found imbedded in the ice in Siberia: from a comparison of its skeleton with those of existing species, Cuvier inferred that this animal must have been antediluvian; and yet, so completely had the cold prevented putrefaction, that dogs willingly ate of the still existing flesh. At St Petersburg, when winter is approaching, the fish in the markets become almost like blocks of ice, so completely are they frozen; and in this state they will remain sound for a lengthened period. Dead poultry, and other articles of animal food, are similarly kept fresh throughout the winter in many rigorous climates, simply by the powerlessness of the attacking agents, when heat is not one of the number. And that which nature effects on a large scale, may reasonably be imitated by man on a more limited one. It is customary to pack many kinds of provisions in ice or snow, either for keeping them in storehouses, or for sending them to market. Thus it is with the tubs of poultry, of veal, and of other kinds of meat, which, killed in the country districts of Russia in autumn, are packed in snow to keep cool till sold at market; and thus it is with much of the salmon sent from Scotland to London. Since the supply of excellent ice from Wenham Lake, commenced about nineteen years ago, has become so abundant and so cheap, it is worth a thought whether the preservative powers of cold might not advantageously be made more available in this country than they have yet been. In the United States, housewives use very convenient refrigerators or ice-boxes, provided with perforated shelves, under which ice is set, and upon which various provisions are placed: a large uncooked joint of meat is sometimes kept in one of these boxes for weeks. Among the celebrities of the Crystal Palace, many will recollect Masters's elegant ice-making machine, in which, by combining chemical action with centrifugal motion, ice can be made in a few minutes, let the heat of the weather be what it may. This machine, and the portable refrigerators manufactured by the Wenham Company, together with our familiar, old-fashioned ice-houses, might supply us with much more preservative power, in respect to articles of food, than we have hitherto practically adopted.

If, instead of watching the effects produced by abstraction of heat , we direct attention to the abstraction of moisture , we shall find that antiseptic or preservative results are easily obtainable. All kinds of bacon and smoked meats belong to the class here indicated. The watery particles are nearly or quite driven out from the meat, and thus one of the three decomposing agents is rendered of no effect. In some cases, the drying is not sufficient to produce the result, without the aid of the remarkable antiseptic properties of salt; because decomposition may commence before the moisture is quite expelled. In many parts of the country, hams are hung within a wide-spreading chimney, over or near a turf-fire, and where a free current of air, as well as a warm temperature, may act upon them; but the juices become dissipated by this rude process. Simple drying, without the addition of salt or any condiment, is perhaps more effectual with vegetable than with animal substances.

But it is under the third point of view that the preservative process is more important and interesting, inasmuch as it admits of a far more extensive application. We speak of the abstraction of air . Atmospheric air affects dead organic matter chiefly through the agency of the oxygen which forms one of its constituents; and it is principally to insure the expulsion of oxygen that air is excluded. The examples which illustrate the resulting effects are numerous and varied. Eggs have been varnished so as to exclude air, and have retained the vital principle in the chick for years; and it is a familiar domestic practice, to butter the outside of eggs as a means of keeping them. The canisters of preserved provisions, however, are the most direct and valuable result of the antiseptic action by exclusion of air.