Tom Tarquinio's longest day at the office ended about 5 o'clock this afternoon when the Naval Academy's understudy quarterback took inventory of his moving parts.

A patch of skin on his lower back might have passed for cube steak, medium rare, and only an autumn sunset in the country carries more lovely purples than decorated the quarterback's right bicep. Curious, Tarquinio poked a finger against his stomach to see how much it hurt in there. Ooouch.

"The second half, it felt like I was getting hit on every play," he said. This was not to complain. Seniors at Navy worry about, oh, Brezhnev's trigger finger but not about itsy-bitsy bruises.

"The line did a great job all day, holding them out. But Notre Dame is a great defensive team and they just keep coming. I'd get the passes off, but they'd be right there pounding me in the chest. Right now, I'd say I'm pretty well beat up."

To get his right arm into the hole of his Midshipman's dress uniform jacket, the quarterback lowered his shoulder instead of raising his pitching wing. He threw 44 passes, the most of his life. He completed 18, one for Navy's first touchdown against Notre Dame in four years.

He threw six interceptions, a school record. One time a linebacker struck Tarquinio's arm in motion and, with the arm as a lever, flipped him pinwheeling until his head clunked against the fake grass of The Meadowlands.

First thing Tarquinio did on arising was wiggle his fingers, the better to see if his arm was still attached because he sure couldn't feel it and he knew he'd be needing it later.

"I wanted to see if it was okay," Tarquinio said, explaining why he went to the sidelines and asked somebody to play catch with him.

Until Navy's star quarterback, Marco Pagnanelli, broke a leg last week, Tarquinio had thrown only 16 passes all season. He threw 18 today after the linebacker stood him on his haircut.

Going against the ruffians from South Bend is a difficult way to break in, because Notre Dame's defenders resemble fellows from an NFL picket line. But Tarquinio, like all quarterbacks, loved the idea, even if it meant he'd hurt a lot later.

His eyes danced with remembered joy when someone asked about Navy going to the shotgun offense in practice this week. Except for the cursed Cowboys of Dallas, the shotgun generally is a weapon born of desperation. You put the quarterback five yards behind the center, giving him an extra second to figure out what to do, and then you throw the ball all over town.

"I was a little hesitant at first," Tarquinio said, "because I'd been mostly a running quarterback in high school. My freshman year at Navy, I learned to drop back. Then, the sprint out. But once we started practicing the shotgun this week, I really liked it. It is good. A good idea."

Good ideas win football games when they are applied muscularly by swift athletes. Good ideas kept Navy within three touchdowns of Notre Dame today. The final score was 27-10. Before Navy scored a safety in the third quarter, Notre Dame had outscored Navy, 98-0, across the last four seasons.

Not that Notre Dame was impressive today. Navy came in hurting, with three veterans unable to play, and quickly today three more joined them in slings and on crutches. Still, Notre Dame led at halftime only 13-0, scoring two field goals in the last 35 seconds. At the mention of Coach Gerry Faust's name on the public address system at halftime, many people in the crowd of 72,201 said, "Boo." They all said it at the same time.

"Robert Hutchins, at the University of Chicago, once said, 'All alumni are dangerous,' " someone said to Faust afterward. "Will this victory be meat thrown to the wolves?"

"Our alumni are great," Faust said quickly, perhaps so quickly as to be judged a defensive reaction. "You guys overexaggerate that. I'm sure there's some disgruntled alumni. But alumni get disgruntled whenever you lose."

A 13-all tie with winless Oregon last week was enough to muss up the gruntles of Notre Dame loyalists. Faust even fell to criticizing the university's student paper, which he suspected of breeding negative thoughts that worked through his charges' musculature until such thoughts rendered the poor fellows comatose. Through six games, they hadn't even thrown one touchdown pass.

Quarterback Blair Kiel ended that foolishness in the second quarter today with a three-yard pass. On the sidelines, Faust excitedly ripped the earphones from his head, raced 20 yards onto the field, spread wide his arms and hugged his quarterback as if they had just earned immortality.

"I didn't even care about that being a pass," Faust said later. "I don't care how they score as long as we get six points."

Tom Tarquinio didn't get his six points until it was 27-2 late in the fourth quarter. On a play called 132 X Deep, he threw one perfectly 45 yards on a line to Bill Cebak diving in the right corner of the end zone. All day Tarquinio had thrown deep, because it was Navy's bold idea to attack a pass defense that Coach Gary Tranquill had declared impervious to attack. Of Tarquinio's six interceptions, three came on passes better left in his aching fingers.

The first 100 passes of Tarquinio's career included only two interceptions. The next 10 passes, in today's third quarter, included four interceptions.

"The second half, there were too many interceptions," Tarquinio said. "I forced a couple I might have shouldn't have. Some of them, we just went deep. And some of them, maybe I should have put more on the ball."

Yes, he knew he had set a record with the six interceptions. "What can I say? You can't worry about making mistakes. If you do, you keep making more."

It was an hour after the game now, and Tarquinio smiled, and then he walked to the team bus, slowly.