A long list of chemical substances have been used from time to time in the preservation of food, but most of them have been supplanted by the safer process of canning, refrigeration, etc.

The use of various antiseptic or preservative fluids is designed to prevent the activity of germs and fermentation. Sugar, like salt, in strong solution possesses decided antiseptic powers, and hence the employment of strong sirups for the preservation of fruits, and of sugar itself in making candied fruits. Other harmless preservative materials which are added are oils, chiefly serviceable for keeping fish, and vinegar and spirits of wine for pickling such products as chilies, tarragon, and shallot.

Vinegar is used to preserve oysters, lobsters, and other sea food, as well as cucumbers, cauliflower, and other vegetables, as "pickles." Spices, mustard, and similar condiments are usually added.

" Soused " fish, such as mackerel, are immersed in mixtures of cider vinegar flavoured with cloves, nutmeg, parsley, bay, onions, etc. After being "soused " once or twice the food is heated in the fluid to 1400 F., flavouring substances are added, such as Worcestershire sauce, extract of anchovy, and lemons, and the whole is put in air-tight jars (Clark).

Among the materials sometimes employed for preserving foods may be mentioned the fumes of burning sulphur (sulphurous acid), acetic acid, weak carbolic acid, bisulphite of calcium, and the injection into the blood vessels of meat of alum, chloride of aluminum, etc. Borax, boric and salicylic acids, formaldehyde, and other materials have been extensively used in the preservation of milk, beer, meats, etc. Sodium sulphite is added to preserve chopped meat and Hamburger steak, and a mixture of borax, nitre, and salt is used in sausages.

A new method of meat preservation has been introduced by a Mr. Jones in England. It consists of injecting the animal the moment after it is killed with a solution of borax, which is so uniformly distributed through the circulation to all the fibres of the meat that but a very small quantity of the antiseptic need be employed.

The use of borax and boric acid as food preservatives is so common that it is a matter of great importance to determine the influence of these substances upon nutrition. This Prof. R. H. Chittenden and William J. Gies have done. (American Journal of Physiology, No. 1, 1898.) After elaborate experiments upon animals, these authors conclude as follows: Doses of borax up to 5 grammes per diem, continued for some time, do not disturb proteid metabolism or general nutrition. In larger doses borax retards proteid and fat assimilation and increases the weight of feces. Very large doses cause nausea, vomiting, mucous diarrhoea, and lessen the urine secretion (through which borax is eliminated). Boric acid in doses amounting to 10 or 15 grains per diem does not affect nutrition or proteid metabolism; it does not affect the volume of urine or irritate the alimentary canal. Neither drug controls intestinal putrefaction.

Later experiments upon man, reported by H. W. Wiley in 1904, show that when either borax or boric acid is ingested with food 80 per cent of these substances is excreted in the urine and 20 per cent in the perspiration. Existing albuminuria is increased by their use, body weight is lost, nitrogen elimination is inhibited, and more phosphoric acid than normal is eliminated.

"Embalmed beef." This term is applied to meat which has been coated with a preservative antiseptic wash of some sort. A solution of boric acid is sometimes employed, but formalin is used more often. Flies avoid the coating and do not alight upon it.

Formaldehyde, or formalin, is a strong antiseptic. It is not especially harmful in moderate doses, but Halliburton, of London, has shown that it is especially active in inhibiting the action of the normal digestive ferments. Given in milk it is injurious to infants.

Glycerin has been used as a preservative, but it cannot be employed in any quantity on account of its aperient action.

It is true of practically all of these latter substances that food preserved by them if used in excess or for any length of time is apt to endanger the normal digestive functions, besides being somewhat less nutritious and more tasteless than other preparations.