The use as a "relish" of the little fish, the anchovy--allied to the sprat and the herring--preserved in salt liquor in a partially decomposed state, but not undergoing the ordinary chemical change excited by the bacteria of putrescence, is remarkable and very widely spread. Anchovy sauce is made by mashing up such chemically decomposed anchovies, and is one of the very greatest and most approved of all sauces. The anchovy is a Mediterranean fish; it is taken in small numbers in sprat-nets in the English Channel and in the Dutch Zuyder Zee. So-called "Norwegian anchovies" are not anchovies, but are small sprats. When taken fresh and cooked and eaten, the anchovy has a very bitter, unpleasant flavour, which can be washed out of it by splitting the fresh fish and letting it lie in salt and water. It was this practice of washing out the bitterness which led the Mediterranean fisher-folk to discover that if left for some time in moderately strong brine the anchovy develops a wonderfully appetizing flavour, and becomes dark red in colour, whilst the liquid also becomes red. I believe that, although it would be easy to do so, it has not been ascertained whether the red colour is due to a direct action of the salt upon the blood-pigment of the fish--as is the red colour of salt beef--or whether it is due to a special red-colour-making bacterium, as is the case with salted dried cod, which is sometimes rendered unsaleable by this red growth. However that may be, the red colour of the preserved anchovy is well known, and is produced by dealers by means of artificial pigments, if not already naturally present in the salted fish as they come to market. No one would guess on tasting a really fresh bitter anchovy that it could develop the fine flavour which it does when soaked in brine to get rid of its bitterness.
Another little fish, the Bummaloh, or "Bombay duck" (Harpodon), is taken in large quantities off the West Coast of India, and is dried and used for the peculiar flavour thus developed, which is quite different from that of the anchovy. It is a deep-water fish, and is phosphorescent. The liking for the flavours developed in these fishes by various bacteria when specially treated, is similar to that which necessity and custom has developed in our attitude to cheese. Fresh cheese is difficult to obtain. Habit has ended in our preferring stale, decomposed cheese, which has developed a whole series of flavours by the action on it of special bacteria and moulds. The Roman soldiers of the first century used a small salted fish (probably enough the anchovy) to eat with their rations of bread, and such fish were usually sold with bread. Probably the small "fishes" which, together with a dozen loaves of bread, are stated to have been used in the miraculous feeding of the multitude by Christ, were salted anchovies.