The two girls, aged 6 and 10, hovered like Munchkin surgeons over the prostrate doll. They probed its stomach with sterile swabs, held an anesthesia mask over its face, squeaked brief orders to each other.

"Is she asleep yet?" asked Johns Hopkins Hospital child life teacher Kathy Johnson, sitting between the two girls.

"No," chirped Dawn Oxendine, 10, of Baltimore, through her surgical mask.

"Check her heart," said Johnson. "Is everything okay?"

"Yep," said Mandy Morgan, 6, of Winchester, Va., pressing a stethoscope to the doll's green terry cloth chest.

The doll lay motionless, its face wreathed in a look of affable confusion.

The two girls, both recovering from genital-urinary surgery at the Johns Hopkins Children's Center here, were using Charlotte, a large Muppet-like doll, to act out the surgery they had just undergone.

"We hope to reduce their anxiety" in case they have to undergo surgery or other hospital procedures again, said teacher Johnson.

"This puts them in control of the situation," she said.

"They're the involved person with control over another person, the doll . . . . It also helps them get rid of any misconceptions they may have about the procedures."

Charlotte, also known as Charlie when her movable body parts are rearranged appropriately, is one of three specially designed dolls the hospital now has for teachers like Johnson to help children overcome their fear of the unknown about hospitals.

The dolls, used both before and after surgery and other procedures, come with detachable scars, tonsils, electrocardiogram attachments, nasal gastric tubes and an assortment of body cavities for filling and emptying as the children see fit.

On the children's cancer ward, one of the dolls, known alternately as Joey or Josie, has bushy white hair that can be peeled off to imitate the hair loss than can accompany cancer treatment.

Dolls for taking the mystery out of hospitals have been used for some time, but a new feature of Charlotte/Charlie is a "raised vein" on the left arm -- a thin plastic tube under the terry cloth skin -- to help children overcome one of the biggest phobias in the hospital: needles and injections.

It's called "needle play." Aided by a teacher, a child finds the "vein," pretends to insert a needle into it, presses the syringe and comforts the doll afterward.

One 15-year-old, recalled child life teacher Renate Flannelly, was "absolutely terrified of needles . . . . Four security guards would have to hold him down" when he came to Johns Hopkins as an outpatient for kidney dialysis, a painful procedure requiring two needles in the youth's arms for four to six hours at a time.

Gradually over an eight-month period of weekly "needle play" sessions, Flannelly said, the boy, who was mildly retarded, overcame his fear by repeatedly inserting a needle in the arm of a doll.

"He needed to be able to jab the doll over and over again," said Flannelly. " . . . Now he comes in and hold his arms out, and the doll has become his friend."

"When children are prepared for hospital procedures," said Jerriann Wilson, director of Hopkins' child life department, "their anxiety may indeed be raised, but then the experience of the actual procedure is not such a surprise."

Children "want to know what is happening."

Demonstrating hospital procedures on dolls "is really important in developing trust," Wilson said.