Zenya Yoshida, for more than a decade Japan's leading breeder of race horses, summed it up nicely.

The Japanese racing fan, he said, doesn't care much about horses. What he does care about is gambling and trying to make money on his bets.

Yoshida's obeservation explains how more than 80,000 people could cram into the lovely Nakayama Race Course here on Toryo's outskirts and create an atmosphere as exciting as an afternoon in the Library of Congress.

Nobody gets very excited at a Japanese track. The crowd watches in silence as the horses come out of the gate. It waits patiently for the stretch run, when it permits itself a murmur of enthusiasm. Then it goes back to the racing tip sheets to prepare for thr next race.

There are no flashy clothes, no boisterous drunks, no delirious winners and no disconsolate losers. Business is business, it seems, and no unexpected frivolity interrupts.

But it is big business growing bigger because Japan has embarked on a sports gambling binge that rivals its earlier craze for baseball. Its 10 national tracks and 33 local tracks draw scores of thousands each racing day and last year the Japanese bet $4 billion at the national tracks alone. In 1966, when the boom was just beginning, only about 2 million people went out to national tracks. Last year's attendance ran over 13 million.

Huge six-to eight-floor betting parlors have sprung up to accomodate off-track bettors, who last year accounted for about two-thirds of all betting on Japan's national races. They are slickly mordern office buildings where bets are totalled by computers, and some handle 100,000 bettors each racing day. Thousands of other gamblers place bets by telephone.

It is largely a postwar phenomenon. Before World War 11 gambling was discouraged by the Japanese government and was discouraged by the japanese government and bore a stigma of immorolity that has not entirely faded away. Horse racing was tolerated only because, it is said, Japan had discovered during the Russian War of 1904-05 that it needed better horses for its army and thought racing might encourage better breeding.

The postwar relaxation of moral attitudes opened the gates for gambling and it was discovered that the japanese were as eager to risk their money as the Americans, French and British. And as the Japanese economy took off in the 1960s, so did horse-race betting. Disposable income rose swiftly in the '60s and '70s and an increasing share of it was disposed of at the tracks. The national and local governments, which receive fixed shares of the betting handles and use them for public services, now encourage the sport.

Even Japan's prolonged recession has not diminished the betting urge. Since the oil shock of the early 1970s sent the economy on a downward spin, the number of persons attending races has levelled off, but the amount of money wagered continues to climb each year. One reason is that the Japanese bettor has a greater chance of winning than in most other Asian countries - by law, 75 percent of the take at national tracks goes back to the national government and the Japan Racing Association, which supervises tracks and all horse gabling under rules laid down by the Ministry of Agriculture and Forestry.

Racing is almost exclusively a man's game in Japan and women are rarely seen at the tracks or in the off-track betting establishments. It is also a young man's game. A survey five years ago discovered that nearly three-fourths of the race-goers were in their 20s and 30s.

The typical fan is a man in his 20s who earns a salary and has no wife or children to support. Officials periodically attempt to transform racing into a "family sport" - all national tracks are equipped with playgrouns and games for childres - but few men bring their families or girlfriends to the track.

The notion that Japanese fans care only about gambling and not about horses is challenged by some racing officials who say that the apparent lack of race track enthusiasm is deceptive. By nature , they contend, Japanese are undemonstrative. Even on sunny days at the track when the finishes are close.

Kinji Ogawa, an assistant general manager of the Japan Racing Association, cites the poignant story of Ten Point as an example of the latent affection for horses in Japam.

Ten Point named after large-sized newspaper until he broke a leg last January in a race at Kyoto. In a rare display of devotion the public sent thousands of messages begging that Ten Point's life be spared. For six weeks, the owners responded by keeping the horse alive through special treatments administered by 36 veterinarians. Well-wishers sent the horse 66 buckets full of "senba-tsuru," the colorful get-well twists of paper usually reserved for ailing humans.

Last Sunday, Ten Point finally died and newspaper treated his death as an occasion for national mourning.

"Rum in Heaven, Ten Point," said the head-line in one Tokyo paper.