The ancients produced from fish two extremely strong seasonings, muria and garum.
The first was nothing but the brine of the tunny, or rather the juice which flowed from it when it was salted.
Garum, which was more costly, is much less well known to us. It is believed that it was made by pressing the seasoned entrails of the scomber or mackerel, but if that were so its high price would not be justified. There is reason to believe that it was an imported sauce, perhaps that soy which comes to us from India and which is known to be the result of letting certain fish ferment with mushrooms.
Analytical gastronomy has long tried to determine what effects a fish diet has on an animal economy and the opinion is unanimous that they are strongly sexual and awaken in both sexes the instinct of reproduction.
Once this result was admitted, it was found that there are two causes of it so obvious that they can be understood by anyone: (1) various ways of preparing fish in which the seasonings are plainly excitant, such as with caviar, picled herrings, marinated tunny, salted cod, stockfish and the like; (2) the various essences with which fish is imbued, which are above all inflammable and which are converted into oxygen and turned sour by the process of digestion.
A still profounder analysis has discovered a third and even more active cause of the sexual effects of a fish diet: the presence of phosphorus, which occurs already formed in the milt, and which always appears in decomposition.