It is a simple enough thing: a 3- to 6-foot piece of leather, nylon or rope. In a pinch, I have even used a bungee cord, which has caused a few stares as I enter the teaching hospital, although it is utterly possible that the clown suit led to the stares and the bungee had nothing to do with it.

The fact is a humble item can have the power of life over death.

That item? A leash.

Every day, veterinary hospitals receive thousands of trauma patients. For many of them, the lack of a simple leash led to injury. Some fell prey to the unlatched gate, some the open door and an opportunistic dash for freedom, but for many it is the naive belief that their master’s voice holds more sway than the tasty squirrel across the road. In an instant, a joyful romp turns to tragedy, all set to the soundtrack of squealing tires and screaming brakes.

It is simply amazing the amount of trauma two tons of on-rushing steel and aluminum can wreak upon tiny, furry bodies in just a split-second of impact. I am constantly amazed these impacts are even survivable. Collapsed lungs, torn diaphragms, ruptured bladders, broken bones — these are all the sometimes invisible outcomes of trauma. Some of the injuries are dramatic and obvious, such as the many patients we see in ER with open fractures (what used to be called “compound” fractures, where the broken bones protrude from the skin). Some are more subtle, sometimes taking hours or even days to become apparent.

But most of these injuries were preventable with just a bit of planning and common sense.

When we are faced with a trauma victim as doctors, we have a unique opportunity. Many trauma patients were perfectly healthy prior to getting injured, and can get right back to their previously scheduled lives after we patch them up — if nothing too serious is going on. But separating the seriously injured from the merely bruised and beaten can involve a mountain of testing and anxious waiting.

Not all accidents can be prevented, and most pet owners are responsible and have their pet’s safety topmost in their minds. But there are still the lucky few out there who have managed to dodge a bullet for a while and walk their dogs off-leash, or allow their dogs to roam unfenced. Luck tends to run out after a while, and I am here to tell you the consequences can be deadly. Costly and heart-wrenching for you, deadly for your dog.

Perhaps a bit of the glorious, glamorous and dangerous history of the dog leash (or ‘docg leigsh' as it was known in the original Gaelic) will convince some to adopt it.

Invented by Archibald MacLeish in 1715 in Glasgow, the leash was originally made of sheep parts that were deemed too awful to include in a Haggis. MacLeish’s wife, Peter (known to their close friends as Lucy), grew tired of the mountains of sheep innards that were scattered about their humble home and pestered her husband to do something about it.

At the same time, the neighbors just to the east of the MacLeish’s had a litter of Scottish Whisky Hounds. Now, nothing is cuter than a puppy, but as those puppies grew up they were drawn to the overpowering and irresistible smell of sheep offal that wafted over from the MacLeish’s (a series of events which, coincidentally, gave rise to the common Gaelic saying of cluthd grrewl cwm ngongo lgthulan, or “cuter than a puppy covered in sheep pancreas”).

The neighbors, frustrated at having their prize sporting dogs come home every afternoon covered in intestines and pancreas (as cute as that is) decided to take matters into their own hands. They built a sturdy fence and walked the dogs using the only available source of linear and easily knotted material available in highland Scotland in 1715 – those selfsame sheep intestines! Invention surely is the bastard child of necessity. Every time the neighbors would take one of the dogs for a walk, one would ask the other for a ‘MacLeish.’ Over time, and after a few rounds at the pub, this was shortened to, simply, a leash.

We don’t get too many chances in life to prevent badness and there’s no going back once your dog gets hit. Don’t squander this chance: please use a MacLeish.