ST. PAUL, Minn. (AP) _ A 6-year-old boy described as a ''tough kid'' has shown steady improvement as he recovers from surgery to reattach his arm and hand, a surgeon said Monday.

Michael Conoboy kept his composure after his limbs were severed Saturday while riding on the long metal arm of an irrigation system in a farm field near his northwestern Wisconsin home, emergency personnel said.

The kindergartener underwent nine hours of surgery Saturday to reattach his left arm, which was severed about 1 1/2 inches above the elbow, and the right hand, which was severed above the wrist.

''He's in critical condition at this point. His condition has improved steadily since Saturday night,'' said Dr. Paul Donahue, who led the surgery team at St. Paul-Ramsey Medical Center.

Michael underwent 4 1/2 hours of additional surgery Monday night. Hospital spokeswoman Robin Rainford said afterward that the Chetek, Wis., boy's vital signs were stable.

She said doctors reattached one artery and two nerves in the boy's right arm.

''They're very pleased with the appearance of the left arm. The right arm is guarded,'' she said.

Donahue said the first week would be the most critical time of the youngster's recovery.

Authorities said Michael and his 14-year-old stepbrother, Matthew Neisler, were riding on the equipment and their clothes became entangled in it.

Matthew, who suffered a bruised wrist, carried Michael and his severed left arm to their home, about a quarter-mile away. An ambulance crew and sheriff's deputies found the right hand in the field.

Donahue said quick thinking by Michael's mother in cooling the severed left arm has improved the boy's chances of being able to use his left arm.

''I do think his left arm will be able to regain some useful functions,'' he said. ''At this point we're not certain he'll be able to regain functions of the right hand.''

Tom Flottum, emergency room nurse at Barron Memorial Medical Center in Barron, Wis., said Michael was ''scared, alert, fully oriented'' when he was brought in.

''He answered all the questions we asked him. He was crying in pain,'' Flottum said. He described Michael as a ''tough kid.''

After emergency treatment at Barron, Michael was flown by helicopter to St. Paul, about 80 miles to the west.

The injuries are similar to those suffered by John Thompson, 18, of Hurdsfield, N.D., whose arms were severed in mid-January in a farm accident involving power machinery. Thompson, who was alone, got into his house and dialed for help with a pencil held between his teeth.

Doctors are optimistic that Thompson, who returned home in late February, will regain some use of his wrists and fingers.