One of my most reliably insightful commenters, Ann, posed a question in the midst of fracas of comments that accompanied my piece on secondhand marijuana smoke in dogs. Here it is.

Question … you wrote, Dr B, that dogs have “exquisitely sensitive lungs.”

This side-comment is what really struck me, rather than the mud-slinging comments pro and con about humans and pot, on this vet blog.

I knew that dogs have a keen sense of smell, but this is the first time that I have read about sensitive lungs. In what ways are the lungs more sensitive, and does that relate to other bodily systems or behavior?

Ann has been commenting for so long, and we’ve been communicating back and forth regularly enough, that I think of her as a personal friend. And she has worked her magic again with this comment.

Here is the context: I had claimed that dogs might be more sensitive than people to second-hand marijuana smoke because their lungs are more sensitive. But what exactly does that mean?

In short, dogs cardivascular and respiratory systems are designed for high performance. Ours, not so much. Dogs’ ancestors’ hunting tactic was simple: Run down prey. (For the record, most scientists believe that dogs descended from wolves.) This involved prolonged bouts of high-speed chase, until the prey was exhausted and caught. The prey was generally fit and built for running as well. This means that dogs’ ancestors had to be extra fit. It was an arms race, with the heart and lungs of predator and prey evolving ever more impressive endurance and performance.

But dogs aren’t wolves. And it’s hard to imagine some Bulldogs running down a ball, let alone a prey animal. But anyone who has seen a Greyhound sprint knows that the cardiovascular and respiratory systems of the species has the potential for exquisite performance.

Contrast that with humans. We evolved for ambush, and we can scurry awkwardly only for relatively short distances. In the world of athletic performance and endurance, even the most fit among us are serious lightweights.

Photo: Doctor helping a dog with lung problemsby Shutterstock

Basically, the heart and lungs of dogs are like a Ferrari engine. Ours are more like a Chevy Nova.

If you put dirty gas into a Chevy Nova, you won’t notice much of a performance change, because there wasn’t much performance to begin with. Smoke-contaminated air is like dirty gas. The generally low performance of the human “engine” is why some of us can get away (sort of) with smoking a pack a day.

But if you put dirty gas into a Ferrari, you can expect bad results and a very expensive trip to the mechanic. The high performance engine is simply more sensitive. It runs best on pure premium.

Thank goodness that dog’s lips can’t accommodate cigarettes or joints. Such a high level of smoke would be utterly devastating to them.

But even secondhand smoke isn’t a good idea. As I said in my original article, why not go outside, or at least open a window?