Biomedical Ephemera, or: A Frog for Your Boils

Other Types of Hair

Aside from scalp hair, humans have four other primary categories of hair:

Lanugo: This is a thick, downy hair, whose name comes from the Latin "lana", meaning "wool". It is present on all fetal humans between approximately 5 and 8 months gestation, and is shed several weeks prior to birth. When a baby is born prematurely, it often has much of its lanugo still on its body. The hair present on the bodies of full-term babies is the much finer and less-insulating vellus hair. Lanugo is also common in the malnourished, making it a key diagnostic in anorexia nervosa.

Vellus Hair: The fine, nearly-invisible, and ubiquitous hair that covers all humans on almost all parts of the body (aside from the lips, palms, and soles of the feet) develops shortly before birth, and continues to cover the parts of the body not covered by androgenic or terminal hair throughout life. Vellus hair is less than 2-4 mm long, and is not connected to a sebaceous gland. This hair also surrounds the scalp hair on the forehead, temples, and neck.

Androgenic Hair: Beginning in puberty, thick, bushy hair begins to develop in place of the vellus hair, in the pubic and axillary (armpit) regions of both genders. In addition, it also develops on the face, chest, and stomach, to varying degrees, depending upon sex and genetics. Androgenic hair follows the same growth cycle as scalp hair, but has a shorter anagen (growth) phase, and much longer telogen (resting) phase.

Terminal Hair: This is the second of the two types of androgen-influenced hair, but it is less "bushy" and dense than what is traditionally considered "androgenic hair". It's colloquially known as "body hair", and develops during puberty, but does not include facial, chest, pubic, or axillary hair. On the legs, arms, and back, thicker, stronger hair grows beneath the vellus hair of childhood and pushes it out, replacing it completely in some parts of the body, and only partially in other parts. In women, the area covered by terminal hair is much smaller, whereas some men (particularly those with Scandinavian, Mediterranean, or Aboriginal Australian/New Zealand backgrounds) can be up to 70% covered in thick, insulating hair. 

Images:

Triplets with Lanugo - Diseases of Infancy and Childhood. Henry Koplik, 1910.

Young Japanese boy, covered in vellus hair - despite the fact that it's nearly invisible, each of us is covered with as many hairs per square inch as our apparently-hairier primate cousins! - Scenes From Every Land. Edited by Gilbert Grosvenor for National Geographic, 1907.

German boxer Max Schmeling, displaying highly developed terminal hair on the arms, as well as androgenic hair on the chest. Library of Congress digital archives. Original from 1938. George F. Bond and Cyril Tuckfield after a rapid buoyant ascent of over 300 feet, after the USS Archerfish bottomed in 1959. Both men have significant terminal hair on the arms and legs. Mark Twain shirtless, displaying androgenic hair - mustache and chest hair.

Top: Canada Lynx (Lynx candensis) Bottom: Bobcat (Lynx rufus)

Despite both being members of the Lynx genus, the bobcat and Canada lynx did are not as closely related as one might think.

The Eurasian lynx (Lynx lynx) first arrived in North America approximately 2.6 million years ago, crossing over the Bering Land Bridge, and moved far to the south, eventually settling in the Southern half of North America and evolving into what we know as the modern bobcat by the time of the earliest human settlers to the land.

During the last Ice Age (22,000 years ago), the Eurasian lynx once again crossed into North America, along with the Homo sapiens who would eventually populate the continent. This second population evolved into the Canada lynx, which is much more closely related to their progenitors than the bobcats are.

The fur patterns of the bobcat vary drastically from region to region. Some southern bobcats are spotted almost identically to the ocelot, while others in the north are much closer to the faded-spot and grey-white coat of the Canada lynx. All bobcats are generally smaller than the lynx, and have tails about twice the length of other lynx species. They're also generally more adaptable, as they will act as opportunistic predators when the need arises.

The Canada lynx can be discerned from the bobcat by, in addition to its size and tail, its distinctive striped ruffed collar, and tufts of fur above the ears.

Wild Animals of the World. Edward W. Nelson for the National Geographic Society, 1918.

Egg of a Phoebe and seven consecutive days of growth.

Phoebes, like most passerines, are altricial birds.

Another way that birds can be classified is whether they're altricial (from Latin alere, meaning "to nurse, to nourish"), meaning they're born helpless and blind, or precocial, where they're relatively mature and mobile upon hatching. 

The spectrum between altricial and precocial is wide, and there's no set formula for which reproductive strategy birds use. In general, though, passerines (the perching or "song" birds), herons, woodpeckers, and birds of prey are altricial.

Book of Birds Common to Town and Country. National Geographic Society, 1915.

The Giant Spider Crab of Japan [Macrocheira kaempferi]

This is a big ol' crab.

Bigger than any other arthropod. Some can be 3.8m (12 ft) from claw to claw.

They're really, really big.

That is all.

Scenes From Every Land. National Geographic Society. Edited by Gilbert H. Grosvenor, 1907.

I think I quite agree with the caption "The best kind of bird on a hat." 

Fashions of the time had largely moved past the curious style of having practically an entire bird on the hat that was so popular at the beginning of the 20th century, but some smaller toques and day hats still featured long feathers. 

A fashionable turn-of-the-century hat for the high-society lady of the East Coast of the United States:

Photograph from Book of Birds: Common Birds in North America. Produced by National Geographic, 1918.