Glynes Graham points to a large rectangular outline on the white wood-paneled ceiling.

“Oh, you can still see it,” she says, pleased.

It’s almost imperceptible. But, like everything else in the building, it holds great historical significance.

It’s the spot where a skylight, now filled in, once cast natural light over an exam table where the veterinarian at the country’s oldest continuously operating practice performed surgery, likely on a horse.

Today, it’s where Graham carries on the tradition of her predecessors by caring for the modern Motor City’s cats and dogs. The exam room is upgraded from the skylight to a 1940s-era light, a metal contraption she refers to as “our most antique member of the staff.”

This year marks the 175th anniversary of Patterson Cat and Dog Hospital, considered Detroit's oldest veterinary practice and the city's oldest operating small business.

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Patterson is celebrating that distinction accordingly, with a July 20 open house that will include a petting zoo, food trucks, popcorn, other animal organizations and the placement of a historical marker above the window on the two-story building’s brick front entrance.

“It’s actually super exciting to own this piece of history,” Graham said. “To be the one who’s kind of kept it going.”

Generation to generation

It was 1844, and there was no electricity.

There was no Ford Motor Company. No Coca-Cola. No rubber bands, postage stamps or safety pins.

James Patterson began taking care of Detroit’s horses and farm animals.

Patterson, an English immigrant, founded his veterinary practice that year in what is now downtown Detroit, somewhere on Griswold Street. It sprung up at a time when horses provided the main form of transportation, and plenty of farmland meant plenty of farm animals.

His son, Elijah Patterson, took over the practice and moved it to an interim location before settling at the current spot, 3800 Grand River, in 1909. The first floor could house 25 horses. Some patients arrived via horse ambulance, a relic now on display at The Henry Ford Museum’s Greenfield Village.

Elijah Patterson’s son, James, took over his father and grandfather’s practice in 1926. Since horses were being replaced by automobiles, he converted it into a small animal hospital with cat and dog kennels, labs and operation rooms.

In 1966, it was purchased by Eugene Miller, who modernized and maintained the operation until 1985, when the clinic’s current owner followed her heart back home to the only place she had ever really wanted to be.

Girl Scout to veterinarian

Long before buying the country’s oldest veterinary practice, Graham was a 15-year-old Girl Scout pursuing her animal first-aid badge.

That’s what first led her to the front door of the Patterson clinic, where she was soon spending every school vacation filing forms, answering phones in the front office, finally assisting in the exam room.

“And I never left,” Graham said.

Well, once, but only for a few years when she moved with her former husband to West Virginia. While back visiting the clinic at Christmas one year, she found out that Miller was about to sell the historic family practice to a group that was consolidating veterinary hospitals across town.

That was all it took. She called her husband and told him to pack.

“I never wanted to do anything other than come here and buy this hospital,” Graham said. “So the minute that was available to me, I was like yep — going home.”

The decision was easy, but the road ahead was not always. There were many lean years when business was slow, so Graham moved in with her parents, unable to pay herself.

At first, people would ask if she was old enough to be a doctor. Many asked to see Dr. Patterson.

“But really, it's me — I’m Dr. Patterson now,” Graham said.

The veterinarian, whose kind face is framed by glasses and silver cropped hair, eased into the role with a quick smile, unhurried laugh and a deep appreciation for the history that came with the business.

Its rich legacy is apparent everywhere — in the 1920s-era built-in kennels upstairs, now filled with antiques and old Christmas decorations. In the old letters she found hidden away, or the silver rabies tag discovered from the 1960s.

It's obvious in the windows on the side of the building where horses once peeked out of their stalls, and the narrow creaking staircase leading to an upstairs that looks like it could be a barn loft.

Mostly, it’s in the clients who say they remember riding the streetcar with their dog to see Dr. Patterson, and the ones she’s seen for so many years that their pets have come and gone and come again. Some clients remember her at 15.

The Patterson Hospital has lived through sweeping changes in Detroit, from horse to automobile and beyond, and now Graham is watching a different change she says is “unheard of.”

Stray dogs used to wander the streets, picked up only by the pound. Now, people call Graham several times a week asking what to do about a dog on the street.

“They’re taking care of dogs and cats in a way they’ve never done before,” Graham said. “It’s pretty amazing the shift, and very noticeable.”

This promising trend in animal care has in part led to more business. The clinic takes five to eight new clients a week, Graham said. She recently hired a second veterinarian to accommodate more patients, and is remodeling to create another exam room.

On a weekday afternoon, Graham sits in an office in the cavernous upstairs. Behind her, the building's only air-conditioning unit is secured to the window frame by pink Hello Kitty tape.

Her white doctor sleeves rolled up, Graham takes a minute out of her packed schedule to contemplate the future of an organization with such a rich past.

“Well, eventually I’ll retire,” she says with a laugh. “And I hope that I have a vet who’s just like me. Who wants to be Dr. Patterson.”

Contact Anna Bauman: abauman@freepress.com; @abauman2