SEVEN 00 am EARLY SATURDAY AND SUNDAY MORNINGS ARE typically the busiest times in an ER for trauma. That's when the bars let out and people put holes in each other and drive their cars down the wrong side of the freeway.

In ER medicine, though, where patients are sick, as opposed to damaged, Mondays usually bring the most business. People procrastinate. They ignore that chest pain and that numbness running along the entire left side of their bodies. After all, the right side feels fine. Why ruin the weekend with a trip to the ER?

Parkland Memorial is a little different. In the ER at Dallas County's only public hospital (and, by the way, one of the most respected in the country), every day is like Sunday morning and Monday combined. Parkland's ER is so busyabout 145,000 patients per year, about twice the number a comparable hospital might handle, many of them uninsured, unemployed-that trauma, medicine, and psychiatry each have their own wing. So on a recent Tuesday morning at 7, when Dr. Mauricio Trujillo begins his 12-hour shift, there are already about 30 patients in the main waiting area. On the medicine side, where he works, 27 more have been assigned beds, some in screened-off rooms. others in the hall.

Trujillo is 29 years old but looks older, which probably has something to do with the stethoscope dangling around his neck. He wears mismatched scrubs, with a green top and blue pants. He has a pair of scissors jammed down the back of his pants, leaving only their plastic green handle exposed above his waistband. The tips of the scissors do not puncture the seat of his pants, presumably, because Trujillo never seems to sit down.

"Who wants some coffee?" he asks, after he's done rounds with the other residents and Dr. Kathleen Delaney, the one attending physician on this shift. "Coffee? You want coffee?" Trujillo is the only Hispanic out of 47 ER medicine residents. He's from Miami, and his parents were born in Cuba. This means he speaks fluent Spanish (and a fair amount of Portuguese), and he brings strong Cuban coffee to work in a thermos. He shares with anyone who can stomach the stuff, pouring it into I-ounce plastic cups meant for dispensing medicine. It's as viscous as dirty motor oil and sweet as cotton candy. "No thanks," Delaney says. "But I'll take a cigar if you've got one."

Properly fortified, Trujillo sees his first patient. Lying on a hall bed, curled up under a sheet, a Hispanic female complains in Spanish about a bilateral pain in her breasts. Trujillo takes her into an exam room with a female escort and emerges a short time later. The patient climbs back onto the hall bed, but now she's grinning.

"She might be pregnant," he says. "The pain is probably due to hormonal changes. A lot of these people, instead of going to Eckerd and getting a $10 pregnancy test, will come see us. We're their primary-care physician."

But why was the woman smiling at him? "Well, there's something else," Trujillo says. "There's a bruise on her breast, and when I asked her about it, she started to laugh. It's a bite mark. Apparently her boyfriend likes to bite her during sex. So that could be part of it, too."

He orders a pregnancy test and hustles off to see his next patient, a 22-year-old black male whose feet are so swollen that they look like loaves of leavened rye bread. He's suffering from nephrotic syndrome. Basically his kidneys aren't working, and his feet are filling up with water. When Trujillo gently squeezes them, the man almost cries. He has been walking around like this for more than a week, uninsured and unable to miss a day of work.

NINE 30 am THERE IS NO RUNNING IN THE ER. FOR ANYone whose notion of emergency medicine has been informed more by ER than by an actual ER, this may come as a surprise. Gurneys rarely slam through swinging doors, with paramedics pushing the things like a four-man bobsled at the top of the hill, shouting out vital statistics. And doctors hardly ever dash over and shout, "Thirty milligrams etomidate IV push, stat!" In fact, the only people who shout in the ER are patients (more on that later), and doctors do a fair amount of standing around, talking, consulting, and - because Parkland's ER is a classroom for UT Southwestern Medical School -teaching.

Bilateral Breast Pain Woman is now back on her very stationary gurney in the hall and snoring prodigiously. She is audible from 20 feet away, where Trujillo and Delaney stand at the nurses' station, an island in the center of the medicine wing. Trujillo might be a third-year chief resident, but he's still got some medicine to learn. Delaney is doing her best to teach it to him, asking him tough questions about Swollen Feet, whom she has just examined. In doctor speak, this is what's known as "pimping" a student.

"Did you take his pants off?" she asks Trujillo.

"Yes. Well, I mean, I pulled them down, not all the way off. I saw his legs."

A brilliant toxicologist of some renown, Delaney has short, matted hair that gives her the appearance of either having recently woken up or just been born, and she wears a permanent frown that suggests (rightly) she is simultaneously working on a dozen patients.

"I get them for not taking their clothes off," she says. "You miss things." She turns back to Trujillo: "This guy is so angry. He's been examined by Chris, by you. Then I come in. He doesn't realize this is the gold exam." They laugh, and she asks Trujillo a series of technical questions about the state of Swollen Feet's kidneys and the medication he's taking in lieu of what he really needs, which is a transplant. Delaney sums it up: "This guy's sick." She says this without irony.

"In the private world, they would check this guy in," Trujillo says. "It's tough. But he's not critical, and we don't have any beds, so we're going to send him home."

ELEVEN 00 am THERE ARE NOW 120 PATIENTS IN THE ER, including those in trauma and the waiting room. A computer system keeps track of every patient, and from one screen Trujillo can scroll through their names to see why and how long ago each was admitted. One man in the waiting room is approaching 10 hours. Beside his name, it says he came in for a refill of Motrin.

The lab results come back on Bilateral Breast Pain. It turns out she's not pregnant. When Trujillo breaks the news to her, she smiles. He tells her she's been snoring, and she laughs.

He pours another round of coffee and grabs the chart belonging to a 57-year-old Caucasian woman who has had trouble breathing for three days. She has red hair and is missing several front teeth. Trujillo listens while the woman describes her symptoms, then asks, "Is anything else going on?"

She doesn't hesitate. "I've had one thing after another go wrong," she says. "My husband passed away in April. I guess it's Murphy's Law. I've just been going on that roller coaster, down to depression. It's been terrible. Terrible."

Trujillo asks if she needs help. She does.

"We are the safety net," he says, after promising the woman he'll take care of her. "That's why I went into emergency medicine. But people won't tell you what's wrong unless you ask."

Bilateral Breast Pain's biting boyfriend shows up and takes a seat next to her on the gurney. She's happy to see him, and they talk quietly.

TWELVE 00 pm FOR LUNCH, TRUJILLO STANDS AT THE nurses' station and eats a Snickers. Second-year residents and interns bring him cases. As he talks them through diagnoses, Trujillo drinks a 20-ounce Diet Coke, compulsively capping the plastic bottle between each sip, until he loses track and tries to drink through the screw top.

TWO 10 pm THERE ARE NOW 156 PATIENTS IN THE ER, which puts the place securely in the realm of "busy." "Crazy busy" happens at around 180. No one has died yet.

Trujillo has in his hands an EKG 12-lead, a length of green graph paper with black lines describing a heart's performance. The lines in this case belong to a 24-year-old black male whose heart is not performing well at all. He was just rolled downstairs to the catheter lab so doctors can get a clearer picture of what's going on, but basically he suffered an acute myocardial infarction or, in Delaney's words, a "big heart attack." Trujillo is using the EKG to pimp two interns.

"This guy's 24," Trujillo says, showing the strip to them. "What do you do, bro?" One intern can tell right away he's looking at a heart attack. The other isn't so sure. "This guy's going to die, dude," Trujillo says. "You need to help him."

It's like showing someone a picture of a house engulfed in flames and asking, "What's wrong with this house?" There's an obvious answer, but only if you know what fire is. The one intern doesn't get it, and now all three of them are laughing.

Trujillo says, "This guy is going, 'Doc, my grandmother's got a pacemaker. Do I need one?"' Now they're cracking up. "Look at his PR interval!" Full-on cackling. And it is funny, as long as it's not your house.