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Vessels and nerves of the choroid and iris
This cutaway diagram clearly shows the position and relation of the sclera to the inner workings of the eyeball.
Comprising the posterior five-sixths of the connective tissue surrounding the eyeball, the sclera is contiguous with the cornea (the anterior one-sixth of the connective tissue) and the dura mater surrounding the optic nerve. Yes, that’s the same “dura mater” connective tissue that’s found surrounding the brain - in mammals, the eyes are simply outgrowths of the brain itself, not independently developed sensory organs (as they are in, say, cephalopods).
Also known as “the whites of the eye”, the sclera is comprised primarily of collagen and elastic tissue, and is a fairly durable and tough outer casing for the inner structures of the eyeball. Directly interior to the sclera is the choroid, which provides much of the structural definition and vasculature of the eyeball, but is very delicate on its own.
Humans are fairly unique among mammals in that the whites of our eyes are always showing. The small size of our irises and the contrast against the sclera allows us to clearly communicate nonverbal (and often subconscious) cues to one another using only our eyes.
Anatomy: Descriptive and Applied. Henry Gray, 1910.
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“The static head breeze. Direct method.”
Static electricity applied to the head via highly-conductive non-contacting crown. Used to “treat” many conditions, from headache to peripheral neuraligia.
Medical Electricity and Rontgen Rays. Sinclair Tousey, 1910.
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Sweat glands in the human epidermis:
Diagrammatically represented (top)
Isolated vertical cross-section (Right)
Isolated horizontal cross-section (left)Staying cool this ridiculous summer, fellow North Americans? Even if you’re hot and miserable and sweaty, your body knows how to keep its organs at the optimal temperature - that’s why you sweat in the heat in the first place!
Unlike other mammals that sweat for thermoregulation (such as oxen and horses), humans largely sweat from their eccrine sweat glands, which are not directly connected to hair follicles. Eccrine sweat glands secrete mostly water, with a few electrolytes (mostly NaCl, which is why sweat tastes salty). The amount we sweat is regulated by the hypothalamus and the contraction of cells surrounding the eccrine glands, and is influenced by hormone release and internal body temperature.
The water secreted by the eccrine sweat glands utilizes a process called evaporative cooling to reduce the surface temperature of the skin, which in turn reduces the temperature of the blood flowing through the expanded arterioles near the skin surface, and that blood flows through the body and keeps the organs and muscles at a relatively constant temperature. Sweat glands are coil-shaped, with a bulbous sac at the bottom that filters blood plasma to produce sweat. When the cells surrounding the sac and coil are triggered, they contract, pushing that sweat to the surface of the skin.
We also have apocrine sweat glands (the only functional thermoregulatory glands in horses and other sweaty mammals), but they’re largely restricted to the armpits, areola, and perianal region. Their secretions are not as simple as eccrine sweat glands - they’re typically milky-white and contain hormones and additional components of blood plasma that bacteria *love* to chow down. Those bacteria produce stinky excretions of their own, and that’s what causes smelly armpits!
When you use deodorant, the substance you apply works by breaking down the components excreted by bacteria that cause the smell, and masking any residual stink that can’t be broken down. Antiperspirants function by plugging the openings of the sweat pores, so that sweat can’t escape. This is usually done with small particles of aluminum. Despite misconceptions, blocking the sweat glands does not cause breast cancer, though some people experience adverse effects due to allergies to aluminum or other ingredients.
Images:
Top: Anatomy, Descriptive and Applied. Henry Gray et al, 1910.
Bottom: Diseases of the skin; a text-book for students and practitioners. J.M.H. Macleod, 1920. -
Japetella diaphana tentacles and buccal cavity
Japatella diaphana is an octopus member of the Bolitaenidae family, and like the other members of its family, is very small - 12 cm long at most. They live, eat, and breed in the pelagic zone of the ocean, unlike deep-sea squid, which rarely spend their entire lives at such depths.
Mature females have a bioluminescent photophore encircling their beak.
Die Cephalopoden. Ewald Rubasmen, 1910.
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![biomedicalephemera:
Young female solenodon at 3-days-old (bottom) and immediately after hairy coat has grown in (top)
The Cuban solenodon (Solenodon cubanus), or almiqui, is one of the few mammals with truly venomous saliva, and is also one of the rarest extant animals on earth. There have been fewer than 37 individuals captured since the species was discovered in 1861. At multiple points in natural history, the almiqui has been assumed extinct, since it had not been spotted in over 50 years (as was the case when it was declared extinct in 1970), or had not been located after extensive professional tracking efforts (as was the case in the early 1990s). However, one individual was photographed by a trained field zoologist in 1999, and an individual known as “Alejandrito” was captured, measured, and released in 2003, and his DNA was confirmed to be that of the almiqui.
The initial cause of “extinction” was likely the introduction of the Asian mongoose around 1550 C.E., which decimated the population in all areas that it was able to access. However, the Cuban solenodon is capable of living at much higher elevations than any mongoose, and has managed to survive the centuries with a tiny breeding population near the tops of the highest peaks in Cuba.
Source: [Solenodon. Glover Allen, 1910.]](http://25.media.tumblr.com/tumblr_m5uvja4bag1qk931ho1_500.jpg)
Young female solenodon at 3-days-old (bottom) and immediately after hairy coat has grown in (top)
The Cuban solenodon (Solenodon cubanus), or almiqui, is one of the few mammals with truly venomous saliva, and is also one of the rarest extant animals on earth. There have been fewer than 37 individuals captured since the species was discovered in 1861. At multiple points in natural history, the almiqui has been assumed extinct, since it had not been spotted in over 50 years (as was the case when it was declared extinct in 1970), or had not been located after extensive professional tracking efforts (as was the case in the early 1990s). However, one individual was photographed by a trained field zoologist in 1999, and an individual known as “Alejandrito” was captured, measured, and released in 2003, and his DNA was confirmed to be that of the almiqui.
The initial cause of “extinction” was likely the introduction of the Asian mongoose around 1550 C.E., which decimated the population in all areas that it was able to access. However, the Cuban solenodon is capable of living at much higher elevations than any mongoose, and has managed to survive the centuries with a tiny breeding population near the tops of the highest peaks in Cuba.
Source: [Solenodon. Glover Allen, 1910.]
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Pangolin - Manis spp.
The eight species of the pangolin genus, Manis, have been the object of curiosity for centuries, but it wasn’t until recently that their true position in the tree of life was understood. As insect-eating creatures that are highly specialized to lick ants and termites (and other nesting insects) from deep inside their nests, they were long thought to be closely related to the giant anteater and other Xenartha. It turns out, however, that this is an example of convergent evolution, where unrelated species develop the same specialization to perform the same function.
Thanks to genetic studies, we now know that the pangolins are most closely related to the order Carnivora. They’re the only extant member of their own order (Pholidota), however.
In addition to their highly-specialized tongues, pangolins have both scales and fur, providing a tough armor on their back and a soft under-belly, allowing them the ability to roll into a tight ball. Their skunk-like scent glands also allow them to spray an acrid deterrent in the face of predators prior to rolling up. Thanks to these defenses, the only serious predators that pangolins face are humans.
Unfortunately, two species of the genus are now known to be endangered thanks to traditional medicine and smuggling. Protection efforts and enforcement in most areas of rural Asia are lacking due to many factors, and habitat destruction combined with continued hunting does not lead to a positive outlook for those species affected.
The Book of the Animal Kingdom: Mammals. W. Percival Westell, 1910.
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Jaws of the Hare
You can see the teeth of the hare in the cutaway of the jaws. Note the “clipping”-oriented incisors, with the grinding-oriented molars. These are very similar to rodent teeth, having continually-growing incisors covered with enamel on the anterior surface, but with exposed dentine on the posterior surface. As dentine wears away much more easily than enamel, it serves as a “self-sharpening” system to keep the teeth in gnawing-condition.
Despite these similarities, the teeth of rodents and lagomorphs are the result of convergent evolution, rather than being closely related. The difference that first led scientists to believe this (before it was proved by analysis of the inner-ear bones and other anatomical features, and, much later, genetics) is that lagomorphia are far more herbivorous than rodentia, and as such, do not have pre-molars, or any evidence of having had them. Their palate anatomy and digestive tract differs significantly because of this.
The Handy Natural History. Ernest Protheroe, 1910.
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Vertical Section of the Sole of the Foot
The stratum corneum is 15-25 layers of dead, hard, keratinized squamous epithelial cells that’s much thicker on the feet and hands than other part of the body. You’ll notice that although there are sweat glands, there are no sebaceous glands or hair.
Stohr’s Histology. Dr. Philipp Stohr, translated by Frederic T. Lewis, 1910.
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The Marmoset
“Marmoset tearing pictures of bugs out of a book and eating them.”
Marmosets have one of the most primitive brain structures of all the monkeys, and are native to South America. Some tribes of Amazonian natives both consume certain marmoset species for protein, while keeping the same species as pets (which are often as much a part of the family as any child).
Big game hunting in Africa and other lands. Axel Lundeberg and Frederick Seamour, 1910.
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Skull of Chinese Water-Deer
Part of upper jaw cut away to show base of tusks.
The Chinese water deer is classified as a cervid, despite having tusks instead of antlers. They are only native to China and Korea, but there are feral populations in pockets of France and southern England.
The New Natural History of the World. Ernst Protheroe, 1910.
