Jockey John K. Adams, the youngest in a family that includes a Hall of Fame rider, was critically injured in a spill during the 10th race yesterday at Bowie Race Course.

Adams, trying for his third winner of the program, had Po Sho 11/2 lengths on the lead down the back stretch when the 5-year-old mare stumbled, throwing Adams. The horse landed on top of the 22-year-old jockey, the third leadign rider at the current meeting.

Adams, who lost sonsciousness, was given emergency treatment and oxygen at Bowie by track physican Antonio B. Valenin. He then was flown by helicopter to the shock trauna unit of the Universirty of Maryland Hospital in Baltimore.

A hospital spokesperson said Adams was in critical condition with chest injuries.

Po Sho broke its left foreleg and was humanely destroyed.

One other jockey, William J. Passmore, suffered a minor injury in the accident when Po Sho's hoffs clipped his back as he tried to avoid the spill aboard Delaware Crossing. He was treated at the track's first-aid room.

Jockey Fred Juen, was forced to check sharply inside the falling Po Sho. He was unseated, but injured.

Adams has been a regular on the Maryland thoroughbred racing circuit for two years. His father was a jockey and his grandfather, Johnny Adams, is a member of racing's Hall of Fame.

His grandfather is now a trainer and last year saddled J. O. Tobin to victory over Triple Crown winner Seattle Slew in the Swaps Stakes. It is the only loss in Seattle Slew's career.

Adams, who has 12 victories since the Bowie meeting opened last month, is considered one of the best young jockeys on the Maryland circuit.

Track spokesman Muggins Feldman said yesterday's spill was the most serious at the track in about 25 years, since a three-horse spill left one jockey paralyzed.