How do you simulate the appearance of a newborn pulled from the womb? Smear a 6-week-old infant with sour cream and jam.

What do you use for a human heart that a surgeon will handle?

Take a scalpel and cut down a cow's heart to the proper size.

These are some of the problems and solutions of dramatizing day-to-day hospital life without ever really giving anyone an injection or sewing a wound.

To simulate an operation, technicians cut into a dummy to create a "surgical wound" that actors can put their hands into, as surgeons would when operating in the chest or abdomen. Technical adviser Barbara Krause mixes a beaker of "blood" from syrup and food coloring and places it out of sight on the operating table so the "surgeons" can dip their gloved fingers into it.

"It gets sticky after a while," she said, "but we usually put vaseline on people's gloves."

The set boasts real operating room lamps and instruments, the most expensive of which is a Gerbode mitral valvulotome, an instrument used in some open-heart operations. Most of the equipment comes from a southern California medical supply company that services both film companies and hospitals.

The emergency room has curtained cubicles containing empty stretchers, waiting wheelchairs, and long shelves that hold boxes of gauze and surgical gloves. A cupboard full of pill bottles and injectable medications stands in one corner. Bottles of intravenous solution fill the cupboards.

When a doctor on the show delivers a baby, the actress playing the mother is always fully draped and the camera never shows the infant's umbilical cord. Krause has tried fashioning fake umbilical cords out of yarn and gelatin, but has decided it is too risky to glue one onto a small baby.

For safety reasons, infants are allowed to stay under the hot lights used for shooting for only about half a minute at a time, Krause said. The casting department therefore often hires twins, or even triplets, to play one baby. Krause said that in past seasons, Dr. Jack Morrison's baby son was played by a pair of twins, one of whom had a cheerful disposition and one of whom was usually in tears. When the script called for the child to cry, technicians stopped the cameras for a moment and substituted the sad baby for the happy one.

When an emergency room scene contains accident victims, the makeup department creates the skin wounds and wardrobe technicians bloody the clothing, with advice from Krause. Wounds often must be exaggerated, Krause said, to make them show up when photographed, such as the facial cuts suffered by Dr. Bobby Caldwell early in the current season.

Some emergency room procedures require special inventiveness. In one episode, doctors tried to revive a patient from cardiac arrest by cutting open his chest and massaging the heart. Technicians prepared a dummy, and Krause helped manufacture real-looking "skin" from gelatin to create the chest wound.

The goal is to be realistic but not overly gory, so that NBC censors will approve each episode. "If it's too, what they would call, disgusting, they don't want to see that," Krause said.

This season, the producers and writers have become increasingly interested in showing visually spectacular medical procedures. Krause obtained a videotape of the actual moment of conception from an in-vitro fertilization laboratory in Chicago for use on one segment. An episode last month showed the interior of the knee joint as viewed through an arthroscope during Dr. Jack Morrison's "knee surgery." (David Morse, the actor who plays Morrison, really did undergo a knee operation this year, although not on camera.)

The "St. Elsewhere" set has special features not standard on television sets, such as ceilings in almost every room and hallway to allow the camera to pan back for long shots along the hospital corridor. Emergency sequences are often shot with a hand-held camera to make them seem more dramatic.

Krause said the key to making the show look authentic is knowing which details can be "fudged" and which are visually important. "I had to get used to realizing what the camera sees and what it's not going to see," she said.