It looks like a samurai sword, and it's almost as long as he is tall. His hands are on the hilt. He raises and steadies the blade.

Two apprentices help to guide it. Twelve years ago, when it was new, this knife was much longer, but the apprentices' daily hours of tending to it, of sharpening and polishing it, have reduced it greatly.

It was made by the house of Masahisa, sword-makers for centuries to the samurai of the Minamoto, the founders of the first shogunate. In the 1870s, when the power of the shoguns was broken and the swords of the samurai were outlawed, Masahisa began making these things, longer and more deadly than the samurai swords of old.

The little guy with the big knife is Tsunenori Iida. He speaks not as an individual but as an emanation, the present voice, of the generations whose blood flows in him and who held the long knife in lifetimes before him, just as he speaks of Masahisa as if he were the same Masahisa who wrought the first samurai sword, in the days of dark mist. Thus it is that he tells me he's been here since 1861, during the Tokugawa shogunate, when this city, Tokyo, was still called Edo.

Iida-san is the master of the house of Hicho, one of the oldest and most venerable of the nakaoroshi gyosha, intermediate wholesalers of tuna, or tuna middlemen, if you will.

The tuna that lies before Iida-san on its belly was swimming fast and heavy after mackerel a few days ago under cold North Atlantic waves. In an hour or so, its flesh will be dispatched in parcels to the various sushi chefs who have chosen to buy it. Iida-san is about to make the first of the expert cuts that will quarter the 300-pound tuna lengthwise.

His long knife, with the mark of the maker Masahisa engraved in the shank of the blade, connects not only the past to the present but also the deep blue sea to the sushi counter.

Everything around him seems to turn still for a breath as he draws the blade toward him and lays open the tuna with surgical precision. And everything around him is a lot, for we are in the frantic heart of a madness unto itself: the wild, engulfing, blood-drenched madness of Tsukiji.

Until the summer of 1972, bluefin tuna was basically worthless to American fishermen. Nobody ever ate it, and its sole commercial use was as an ingredient in canned cat food. The only tuna that people ate, the white stuff, also in cans, was processed from smaller, albacore tuna, and even that probably would not have gotten into the American diet if a California cannery hadn't run out of sardines and begun selling it in 1903.

Theodore C. Bestor is the author of Tsukiji: The Fish Market at the Center of the World, the standard work on the subject. He, the chair of the Anthropology Department of Harvard, and I, the chair of nothing, spent some time together in Tokyo. It was Ted who taught me how to correctly pronounce the name of this place: "tskee-gee." (In her new book, The Sushi Economy, Sasha Issenberg says it's "pronounced roughly like 'squeegee,'" but it's not. Her book, however, is an engaging one.)

"I grew up in central Illinois," Ted told me, "and as a kid I don't remember ever eating fresh fish. I'm not sure I ever even saw one. As far as I knew, fish came frozen, already breaded and cut into oblongs for frying. And tuna, of course, was something that appeared only in cans like hockey pucks and ended up in sandwiches. I had absolutely no idea of what a tuna looked like, its size or anything else."