Thursday, November 14, 2013

Armies of finger bones

I recently finished an editing assignment that had to do with the bones and musculature of the hand. The bones of the fingers (and the toes, as it turns out) are collectively called the phalanges. They're individually identified by which finger or toe they belong to and by their position. The proximal phalanx is the first one out from the center of the body (or more immediately, from the hand or the foot), the intermediate phalanx is the next one out, and the distal phalanx is the bone at the end of the finger or toe. The thumb and the big toe have only proximal and distal phalanges. I did not know that my little toes have three bones each.

Note that the singular of phalanges is phalanx. You may be familiar with this as an army formation used by the ancient Greeks in which several rows of soldiers stand close-packed side by side—just like the close-packed rows of finger bones and toe bones do, hence their name.

The word proximal is related to proximity, which both come from the Latin root proximus, meaning nearest or next. In anatomy, it's used to describe something that is closer to the center of the body or some other point of origin, such as where a muscle attaches. Distal was formed from distant plus the suffix -al to describe something that's furthest away from wherever the zero point is.

Distal was modeled after other anatomical terms: proximal, obviously, but also ventral and dorsal, among others. Your dorsal side is your back side; in Latin, dorsum means back. In the square dance step do-si-do, partners briefly dance back to back, which is what the original French term dos-à-dos means. The phrase was weathered down to do-si-do by English speakers.

Dorsal can also refer to the side of a particular organ or structure that is closer to the back, in humans and other animals. Note that in a quadruped or a fish, the dorsal side of something, or a dorsal structure, is going to be at the top, not the rear (think dorsal fin). This is why the upper surfaces of the hands and feet are called the dorsal surfaces. (I'll try to remember to use this the next time I drop something on my foot.)

Your ventral side is your front side, or the side where your belly is. The Latin word for belly is venter, which made it into French and Spanish as ventre and vientre, respectively. The Frence phrase ventre à terre is sometimes used in English. This idiom translates literally as belly to the ground, and if you're traveling ventre à terre, you're going very fast indeed.

Before Eadward Muybridge's freeze-frame snapshots of running horses, an artistic convention for indicating that a horse was galloping flat out was to show the animal with its front legs reaching out in front of it and its hind legs stretched out behind it, as if the horse was in mid-leap; this left its belly closer to the ground: ventre à terre. Muybridge, of course, showed how a horse really gallops.

It's possible that my dreams will be haunted by armies of fingers, but I'm hoping for square dancing or even galloping horses instead.


Tuesday, November 5, 2013

Woolly bears and northern stars

Woolly worm season is upon us. The other day I spotted one of these fuzzy caterpillars behind my car, and I moved it to avoid backing over it. Woolly worms were one of the many surprises that awaited me when I moved to Indiana. The first one I ever saw was hitching a ride on a letter I was pulling out of the mailbox; it surprised me considerably, not least because I'd never seen anything like it in the desert where I came from, and certainly not in the mailbox.

What it was doing there I'll never know, but it was probably looking for a peaceful dark place to spend the winter. The woolly worm is the larva of the Isabella tiger moth, Pyrrharctia isabella. It's also called the banded woolly bear. The second generation of each year overwinters as caterpillars, generating their own antifreeze to protect themselves from damage due to freezing, and pupates in the spring, becoming a nondescript pale orange moth.

The caterpillar, on the other hand, has a distinctive pattern of coloration, appearing a coppery orange in the middle and black at the ends. The width of the central band varies, and folk wisdom says that it indicates how severe the coming winter will be. However, this is no more than a charming folktale, autumn's counterpart to Groundhog Day. The width of the stripe varies with the age of the caterpillar and how well it has eaten.

Many of the tiger moths have fuzzy caterpillars. These moths belong to a family called Arctiidae, although some taxonomists have proposed rearranging the family tree so that they belong to the subfamily Arctiinae in the family Erebidae. Either way, the family or subfamily takes its name from the Greek word arktos, or bear, because the caterpillars are collectively known as woolly bears.

We also see this Greek root in the word arctic, which comes from arktikos, meaning of the bears. The bears here are the northern constellations that today go by the Latin names Ursa Major and Ursa Minor; they contain the Big and Little Dippers. There's also a star called Arcturus; the name can be translated as the Guardian of the Bears, and evidently was given to the star for its position in the sky not too far from the starry Ursae. It's just another example of the wide range of some Greek roots.

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