JOCK SEMPLE is Scottish with an Irish temper, and if you tell him you're from Harvard and that you want to enter his Boston Marathon, he will regard you with an instant hate. This means that Jock Semple has a lot of hating to do because last year about 30 Harvard students decided the famous Marathon was at least worth a laugh, and probably quite a few more will send in entry blanks for this year's event. But the thrill of running in the Marathon is worth the price of incurring Jock's wrath.

The famous race used to attract only 200 runners each year, but the recent jogging craze has caused applications to mushroom, and this year Chairman Will Clooney encouraged only those who felt they could finish within four hours to enter.

Another reason for over-application is the college crowd. Jock made his stand known quite unambiguously in a newspaper last April. "It's those jokers from M.I.T. and Harvard that drive me nuts. You know, the ones with the funny hats who run for fraternity stunts," Jock proclaimed. He probably won't be too very pleased if and when he learns of the competition between the Crimson and the Yale Daily News.

The Marathon represents all the euphoria in the Boston area, all the class. It's like lying by the Charles on a sunny day, riding a bicycle out to Wellesley, or eating baked beans. It falls on Patriots' Day in the wonderful state of Massachusetts, and scores of people line the streets to watch friends and some good runners pass by. Patriots' Day is April 19th, but this year the race has been moved to April 21. Strangely, Harvard does not honor this holiday.

And the Marathon is probably your best entertainment value in the area. Assuming you are registered with the AAU, which requests $1 for the honor of membership, you pay only $2 to enter the Marathon and here is what you receive: bus ride to Hopkinton, numbers and pins, dressing facilities at Hopkinton Junior High School, 26 miles of open concrete, dressing facilities in the Prudential, and best of all, tasty beef stew in the Pru afterwards. And of course, while you're receiving all these benefits, you enjoy a healthy run as well.

HALF THE excitement of this festive affair is the time leading up to it when you train, if that seems necessary, and get yourself psyched for the big way. Around Cambridge, it's especially enthralling. The Charles is a spawning ground, rather a training place, for an enormous number of marathoners and a fair amount of regular old runners, too.

As you run by them you may either flash the warming smile as if to say, "Isn't jogging refreshing and aren't a lot of people missing something," or else you stare him down, a warning to look out for you in the Marathon because "look how fast I'm runing without even breathing and I can go so much faster." At any rate, you contemplate the runner, figure htat he'll be at the starting line, and wonder if you can beat him. Man is a competitive animal, remember.

But while one may conjure up idyllic images of smiling people merrily skipping on the river banks in preparation for a slightly more strenuous workout on Patriots' Day, it should be mentioned that marathoners are usually plagued by physical problems. Legs, of course, can act up, knees can rattle around, and calves often tighten.

Though these are dangers, it is his feet that a distance runner must normally be most wary of. With step after step on the concrete, one can only expect some reaction in terms of blisters. They crop up on the balls of your feet, heels, and arches; sometimes elsewhere. These must be worried about continually and dressed up in band aids, tape, or the wonderfully helpful Dr. School's Moleskin.

I've often been tempted to go lay a big juicy kiss on the 60-year-old lady in the College House Pharmacy who gave me my very own box of Mollskin on a fateful day last spring. Blisters had been a terrible problem for me, but after my trip to the Pharmacy, life for my feet was immeasurably better. A good deal of any success I had in last year's Marathon must be credited to the little old lady.

Blisters have been my only difficulty this year, too. One day, the feet are fine. So you run a long workout. New blisters develop or old ones recur. An easy day, then you feel better, and you try again. Blisters. It seems a fact of life for the marathoner, but it's minor after all. Blisters, not life.

I first considered running in the Boston Marathon while I was a senior in high school listening to the coverage of the race on the radio. It was run in 45-degree, rainy weather. I quickly decided that since I was going to be in the area the next spring and that I would be old enough (18 years), the Marathon was a necessity for me. The idea of running 26 miles, in the rain yet, was just insane enough to be tasteful.

One day in March, 1968, I telephoned the sponsoring B.A.A. to tell them I'd be there on Patriots' Day. I was greeted, if that's the appropriate word, by that Scottish voice so familiar to runners around Boston. I was talking to Jock Semple. I felt a certain sense of excitement. But I didn't give him the satisfaction of letting him know that I knew who he was. "I'd like to run in the Marathon. What is the procedure for entering? I'm a college student."

Nothing that I said appealed to the great master. "What makes you think you can run 26 miles? Have you ever done it before?" Jock was reacting to the record field of 1100 entrants.

"Well, no, but I'd like to try." Jock had every reason to hate me, from his point of view anyway, and I'm sure he did. Nevertheless, he told me what I had to do to run in it, and I had jumped my biggest hurdle.