Biomedical Ephemera, or: A Frog for Your Boils

Scabies mites (now known as Sarcoptes scabiei), cross-section of burrow tunnel in skin, and lesions caused by infection

Scabies is a very contagious parasitic skin infection, caused by a mite closely related to the one that causes sarcoptic mange in animals. Just like in mange, the primary symptoms are intense itching and lesions/hair loss where the mites have burrowed.

While the scabies mite causes skin damage and flaking, the intense itching, swelling, and oozing of wounds is caused by allergic reaction to the mite feces - that’s why when someone comes in contact with an infected person for the first time, they often don’t experience symptoms until two or three weeks after the mite has colonized their skin, while subsequent infections will cause symptoms within hours or days.

Infection by scabies is one of the most common dermatological conditions of childhood, second only to head lice. The most common site of lesions is on the wrists and hands, though the mite can colonize almost any part of the body. While it’s a highly treatable condition, using common anti-parasitics such as ivermectin, if exposed family members are not treated and if bedding and clothing is not sterilized during treatment, re-infection is common.

Diseases of the Skin, Their Pathology and Treatment. Milton B. Hartzwell, 1919.

Anatomy and Position of the Kidney in the body

The kidney is a fascinating and under-appreciated organ. Even its name is interesting: while the Greek nephros and the Latin renes are both used as medical terms for the kidney and its anatomy, the origin of the common name in English - "kidney" - is actually unknown. It may be from the Old English terms cwið (womb) + ey (egg), from its shape, but there is no clear consensus on its origins.

The kidney serves many functions, but its most obvious is creating urine. The process of doing that is surprisingly complex, and involves regulation of blood pressure, re-absorbing vital nutrients, excreting urea from protein catabolism, and secreting hormones such as erythropoietin (which stimulates red blood cell creation).

These are four major sections of the kidney:

Anatomy: Descriptive and Applied. Henry Gray, 1918.

The problem doesn't come when the mother is a different ABO blood type from her babies, thankfully! The problem only comes when the mother is a different Rh (or sometimes other) blood type from her babies.

Say a mom is O-. If her partner is A+, and the baby is A+, she's probably going to gestate that baby without problems, and then deliver it without problems. The ABO antigen is too large to pass through the placenta, and even though the Rh factor antigen (the + and - in the blood type) is small enough to pass through the placenta, if she hasn't been exposed to an antigen previously, she won't have a negative reaction to it. So she'll deliver the first baby without problems.

After that, she'll probably gestate the next baby without too many problems, but upon delivery, assuming some blood transfer, there could well be immune reactions on both ends of the equation - there's the possibility of both the mother and the child (though the mother is at a higher risk) having a negative reaction to birth. She already has antibodies ready to attack the Rh "antigen". This is why Rho(D) immune globulin is administered when the mother's Rh factor is different from her baby's.

Until about 1955, the majority of [second or beyond] infants with Rh factors different from their mothers had either chronic health problems, or passed away within the first few days of life due to the anemia caused by the destruction of erythrocysts (erythroblastis fetalis) but since the discoveries of the 50s, the majority of people born or giving birth to those with different blood types, have not died from that cause.

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.

Autopsy No. 98 - Mucosal Inflammation and Hemorrhage in Influenza

Drawing of a section through a trachea showing necrotizing hemorrhagic inflammatory process of the mucosa. Patient otherwise healthy young male. Contracted influenza December 1919.

One of the more interesting points of the 1918 flu pandemic (otherwise known as the Spanish Flu) is the cytokine storm process that killed so many of the healthy young adults who contracted it. Their immune system was strong and reactive, and would respond to invading pathogens by launching a massive attack. Normally, this would have been good, but the H1N1 flu strain was (and is) known to induce a much larger reaction than was necessary. The immune system, instead of just killing invaders, would end up overwhelming the patient, and symptoms resulting from that over-reaction (such as hemorrhage and edema in the lungs) were the top killers of healthy adults who contracted the disease.

One of the primary symptoms of the 1918 H1N1 virus was that the cytokine storms combined with the infecting pathogen ended up as a uniquely hemorrhagic influenza. There were even large numbers of reports of people hemorrhaging from petechiae on the skin, in addition to the intestinal, tracheal, and mucous membrane hemorrhages that were widespread. Hemorrhaging from the pleurae of the lungs was particularly fatal.

Pathology of Influenza. Charles Winternitz, Isabel Watson, and Frank McNamara, 1920.

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.

Right lung with surface hemorrhages

Lung moderately enlarged due to influenza. Note the consolidation of infectious activity in the blue area.

The Pathology of Influenza. M. C. Winternitz, Isabel M. Wason, and Frank P. McNamara, 1920.

Section of trachea showing necrotizing hemorrhagic inflammatory process of the mucosa

Happy flu season!

The Pathology of Influenza. M. C. Winternitz, Isabel M. Wason, and Frank P. McNamara, 1920.

Early Bronchiolar Lesion in Fatal Influenza

You can see the mucus in the lumen (that open area in the middle), preventing air exchange. There is also inflammation present.

The Pathology of Influenza. M. C. Winternitz, Isabel M. Wason, and Frank P. McNamara, 1920.

Toxemia of Pregnancy [this liver damage caused by HELLP Syndrome - "hemolysis, elevated liver enzyme, low platelets"]

You can see the breakdown of the liver where incoming toxins and dead tissues are taken up to be processed (around the central vein, which is in the center of that deeper red area at the bottom). When the liver is overwhelmed by all the incoming toxins and dead cells, the liver cells themselves start to die, as they're destroyed by what they'd normally be able to neutralize. This liver lobule still had normal liver cells on the surface, but would have had little to no processing ability to eliminate toxins in the blood. When the liver fails, death is often not far behind.

The Practice of Obstetrics, Designed for the Use of Students and Practitioners of Medicine. J. Clifton Edgar, 1907.

Cross-section of a human tooth-germ

You can see all the layers of the developing tooth here. All the way to the right (i), you can see the tooth-sac that the developing tooth is surrounded by and nourished by. In the center (f), you can see the developing enamel (though it's still gelatinous at this point) - h signifies the outer epithelial cells of the enamel, which will comprise the outside of the tooth when it's fully formed. To the left, b signifies the odontoblasts (the cells that are precursors to the inner tooth structures), and a signifies the tooth-papilla, that the odontoblasts will expand into.

The tooth-germ starts like a cup, basically, and then expands both outward (to form enamel), and inward (to form the dentin and inner structures) at the same time. 

Atlas and Text-Book of Dentistry, Including Diseases of the Mouth. Gustav Preiswerk, 1906.