Interspecies Physical And Metabolic Similarities
“Is that the same as people amoxicillin?” Mrs. Jones asked.
It’s a logical question, since most people are under the mistaken impression that there are a lot of differences between people and animals.
I learned of mammalian anatomical similarities when I took a trip to Washington, D.C., between my freshman and sophomore years at Auburn University’s College of Veterinary Medicine. One of my favorite sights was the Smithsonian Museum of Natural History. Fresh out of a year of anatomy class and anatomy lab 22 hours per week, I could name every bump and curve on every bone of the body.
Imagine my surprise, then, when I saw dinosaur bones, millions of years old, almost identical to the dog, cat, cow, horse and bird bones I had just studied.
That still ranks as one of the most startling revelations of my life.
Even more amazing to some folks is that, though we are higher on the evolutionary ladder than our pets, our physical and metabolic similarities are striking. The main things that separate us from them are our brain power, our vertical stance and our lack of hair-covering.
Since we have mostly the same bones, the same internal organs and similar metabolisms, let’s look at some differences.
We walk on our metatarsal bones. Dogs and cats walk on the junction of the metatarsal bones and the phalanges, or “toes.” We call that junction the “ball” of the foot. The big toe, or first digit, is missing on the rear feet of most pets unless they have “dewclaws.” The same bones are in their feet and ours, pets’ bones and people’s bones just have a different relationship with the floor.
Heart, lungs, kidneys, pancreas, spleen, stomach and intestines all look and work about the same in domesticated animals and humans.
Metabolically, the differences are mostly in degree. A dog’s heart rate depends on its size, with larger dogs’ resting rates averaging 45 at rest while smaller dogs may exceed 150 beats per minute. It is not uncommon for a cat’s heart rate to exceed 160, even at rest.
The liver of dogs and cats is the internal organ most different form a human’s. Under a microscope one would be hard-pressed to tell the difference. In all species the liver is charged with detoxifying certain poisons and medications and it is there that the biochemical differences are striking. Ignoring those differences could be fatal.
For example, a cat should never receive acetaminophen (Tylenol®) because its liver lacks the ability to detoxify that commonly-used “people” medication. Both dogs’ and cats’ livers have difficulty detoxifying ibuprofen, also.
Now, back to Mrs. Jones’ question about “people” amoxicillin: Amoxicillin is an antibiotic. Antibiotics are not chosen according to which species they will be used in, rather the choice is made according to the type of bacteria are to be killed, and in what part or organ of the body those bacteria reside.
For example, say you and your dog both had identical bacterial infections of the kidney. It is highly likely that your physician and your veterinarian would choose the same antibiotic to treat you and your dog.
However, if those same bacteria were infecting your prostate gland and your dog’s prostate gland, the antibiotic chosen for the kidney infection would be unlikely to work, as antibiotics perform differently in those two organs. Still, you and your dog would probably take the same antibiotic for your prostate infections.
Furthermore, only amoxicillin is amoxicillin. If “people” amoxicillin were different from “dog” amoxicillin, they couldn’t both be called amoxicillin.
No question, you are wonderfully and fearfully made. As are your pets.
And that is yet another way that we are very similar.