WITH THE TOWN given over to drunks this Sunday -- we intoxicates made lightheaded with the emotional champagne of running the 26-mile Marine Corps marathon -- the sober spectators shouldn't feel left out. Your sport, though less taxing of muscle and wind, is to strain your eyes to watch the pack pass by and figure out the varied species.

From what I've seen, after several years of both watching races and watching spectators watch us runners watching spectators, about five major species -- all of them emphatically unendangered -- are on the loose.

The Old Pro Runner: You know this fellow by his black socks, faded Bermuda shorts and plaid farmer's shirt. He dresses down for running, not up, like the mobs brought out by the running boom books who think marathons are fashion parades. Black socks and Bermuda shorts were good enough in the old days, they are good enough now. Not for the Old Pro the velour sweatshirt and terrycloth sweatband. Those degeneracies are for people who see Farrah Fawcett as America's greatest runner.

The prime vantage point for catching the Old Pro is after the 20-mile mark. In this stretch, he is joyously passing the veloured whose high-priced high fashions are suddenly powerless against the might of The Wall. If he says anything as he presses past, it is the ancient truth of the marathon: The race doesn't begin intil the 20-mile mark.

The Carbohydrate Loader: In the last three days, he's put away 10 pounds of spaghetti. That's how the top runners get ready, he explains over dinner to his family, which never wants to eat spaghetti again after three nights of it.

You will know The Loader by his bloated, trudging running style. He can't help it. His lower intestines are so crammed with spaghetti that by the second mile he feels as though he is carrying a low-slung backpack, except it's inside.

The portable toilets along the course are for the benefit of The Loaders to unload. Some won't want to sacrifice the time, so they will gut it out, hurting in the bowels, not the hamstrings like everyone else. After the race, the Loader wonders to himself: If spaghetti is needed for distance running, why aren't Italians winning all the marathons?

The Would-Be-Mystic: He took up running after reading Dr. George Sheehan, the celebrated Irish poet-philosopher who has had as many mystical visions in marathons as all the sainted Teresas, Joans and Catherines ever had in their cloistered convents. By the 13-mile mark, this fellow begins getting nervous: I'm halfway there -- where are the visions?

The only mystical experience so far occurred when he ran through Georgetown and the heavenly aroma of fresh-baked bread, wafted out of the new M Street market. The bread of angels, he thought to himself while imagining that his mind was in the lotus position.

Then he tripped on a cobblestone and inhaled the odors of the garbage cans behind Cannon's fish store. St. Teresa never had to contend with this.

Grandpa and Grandma: "It's never too old to start jogging," says 93-year-old Gramps to his child bride of 89 as they bring up the rear of the pack. They took up running in the physical fitness boom begun the other day by Theodore Roosevelt.

Like most old-timers, Gramps likes interviews in which cub reporters ask for the secrets of longevity. "Sonny, it's lots of whiskey, cigars and running. The last cancels out the first two."

It is proper to cheer loudly for Grandpa and Grandma, except it is people like them who are driving up the costs of the nation's health care bill. They don't die cost-effective deaths. It takes 10 or 15 years for runners to die. Intensive runners, the tab picked up by the Medicare, Medicaid and Blue Shield. The smokers and drinkers should be thanked for their patriotism: They die fast, almost on their feet.

Unbeknownst to the reporter, Grandpa and Grandma get $100,000 a year in under-the-table money to run in marathons. Shoe companies put up some of it, trade associations for alcohol and tobacco the rest.

The Battle-Hardened Marine: With shaven head and stiffened spine, Col. Blood-and-Guts defines the marathon as 26 miles of boot camp. Except it's gone soft, befitting these permissive times when not only Commies but mullahs push us around and the helicopters don't work. If this was really a race for Men, says the Battle-Hardened Marine, the course would include running up the stairs of the Washington Monument, which comes between the 10- and 12-mile mark. Then the course would go through the Reflecting Pool, not alongside it.At the 20-mile mark, have a real wall -- the 12-foot kind from boot camp. If you can't scale it, you're out of the race and shipped back to Parris Island. Then, for the last four miles, you take of your running shoes and put on steel-toe fatigue boots.

All this is for just the Marines in the race. The rest of us -- softies all, with as little hair on our chests as Marines have on their heads -- still run under the illusion that the marathon is tough.