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• Pain Index 1.0 - Sweat bee: Light, short-lived, almost fruity. A tiny spark has seared a single hair on your arm.
• Pain Index 1.2 - Fire ant: Sharp, abrupt, mildly alarming. As if walking across a shag carpet & reaching for the light switch.
• Pain Index 1.8 - Bullhorn acacia ant: A rare, piercing, advanced sort of pain. Someone has fired a staple into your face.
• Pain Index 2.0 - Bald-faced hornet: Rich, hearty, slightly crisp. Similar to getting your hand squeezed in a revolving door.
• Pain Index 2.0 - Yellowjacket: Hot and smoking, almost irreverent. Imagine W. C. Fields blowing out a cigar on your tongue.
• Pain Index 2.x - Honey bee and European hornet: Like a matchhead that flips off and burns up on your skin.
• Pain Index 3.0 - Red harvester ant: Bold and unforgiving. Somebody is using a drill to excavate your ingrowing toenail.
• Pain Index 3.0 - Paper wasp: Caustic & burning. Distinctly bitter afterimage. Like running out a beaker of hydrochloric acid on a paper cut.
• Pain Index 4.0 - Tarantula hawk: Blinding, ferocious, shockingly electric. A running hair drier has been dropped down into your bubble bath.
• Pain Index 4.0+ - Bullet ant: Pure, acute, bright pain. Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel.

Neurosyphilis refers to a site of infection involving the central nervous system (CNS). Neurosyphilis may occur at any stage of syphilis. Before the advent of antibiotics, it was typically seen in 25-35% of patients with syphilis.

Neurosyphilis occurs about 10 to 20 years after first being infected with syphilis. It is considered a life-threatening complication of syphilis. Not everyone who has syphilis will develop this complication.

There are four different forms of neurosyphilis:

* Asymptomatic
* Meningovascular
* Tabes dorsalis
* General paresis

Asymptomatic neurosyphilis occurs before symptomatic syphilis. Signs of the disease may be seen in the spinal fluid, but the person has no symptoms.

Meningovascular neurosyphilis causes nerve and eye problems, among other symptoms. There may be damage to the blood vessels, which can lead to a stroke.

Persons with tabes dorsalis have damage to the spinal cord that slowly gets worse, making them unable to walk.

In general paresis, brain cell damage causes paralysis, tremors, seizures, and mental decline. Inflammation may occur anywhere in the brain or spinal cord and can lead to a number of neurological problems.

* Headache
* Stiff neck
* Irritability
* Poor concentration
* Mental confusion
* Depression
* Visual disturbances
* Abnormal reflexes
* Abnormal gait (walk)
* Incontinence
* Dementia
* Weakness, numbness of lower extremities
* Loss of muscle function
* Muscle contractions
* Muscle atrophy

Note: There may be no symptoms

First, William Shakespeare wrote, in The Life of Timon of Athens, referencing the venereal nature of syphilis:

This fell whore of thine
Hath in her more destruction than thy sword,
For all her cherubim look."

Second, Isaac Asimov wrote in Limericks, under "Luetic Lament,":

There was a young man of Back Bay
Who thought syphilis just went away.
And thought that a chancre
Was merely a canker
Acquired in lascivious play.
Now first he got acne vulgaris,
The kind that is rampant in Paris
It covered his skin
From forehead to shin
And now people ask where his hair is.
With symptoms increasing in number,
His aorta's in need of a plumber
His hear is cavorting
His wife is aborting
And now he's acquired a gumma.
Consider his terrible plight -
His eyes won't react to the light
His hands are apraxic.His gait is ataxic.
He's developing gun-barrel sight.
His passions are strong as before
But his penis is flaccid, and sore.
His wife now has tabes
And sabre-shinned babies
She's really worse off than a whore.
There are pains in his belly and knees.
His sphincters have gone by degrees.
Paroxysmal incontinence,
With all its concomitants,
Brings on quite unpredictable pees.
Though treated in every known way,
His spirochetes grow day by day.
He's developed paresis,
Converses with Jesus,
And thinks he's the Queen of the May."

This poetic manifest reveals the myriad of sickening phenomenon arising from this chronic, indolent infection.

Heat shimmers in the air, distorting the tan grass and gray-green, scrubby trees near a family of African elephants. They graze languidly, catching what shade they can from the sparse trees. Suddenly they all lift their heads in unison, flop their big ears forward and begin to march away, as if alerted by an inaudible air raid siren. Miles away they blend with another group.

A bull in musth—physiologically ready to mate and searching for a female—mysteriously avoids other males, but marches miles directly to a female in heat. Old Africa hands used to call both these phenomena “elephant ESP.”

A scientist studying the movements of elephants he has fitted with radio tracking collars documents the odd coordination between families of cows and calves. He repeatedly tracks two separate groups moving in unison, for hours, days and even weeks at a time. They turn together, maintaining parallel tracks miles apart. Sometimes the groups simultaneously change direction, moving directly toward each other and blending. While the elephants likely use their keen sense of smell when they can, the wind often carries odors in the wrong direction, so the scientist concludes smell alone cannot account for these coordinated movements.

Several bulls dip their dusty trunks into a water hole, in Namibia’s Etosha National Park, savoring the stark contrast to the parched air they breathe. Suddenly two look up, spread their ears wide and crunch more than half a mile through the brush to find not a female in estrus, but a pair of biologists and a Volkswagen van with a huge speaker mounted on top. The elephants, possibly taken aback, march on past. The biologists, Loki Osborn and Russel A. Charif of the Bioacoustics Research Program at Cornell University, watch with relief. They had broadcast a call recorded from a female in estrus, but neither they nor the rest of their team, videotaping in a tower near the water hole, heard a thing. The sound, below the lower threshold of human hearing, forms part of the remarkable infrasonic communication system of elephants.

Humans can hear many elephant calls, from the famous shrill trumpets to low groans. But until Katherine B. Payne of Cornell analyzed a tape she’d made of Asian elephants at Portland, Oregon’s Washington Park Zoo, no one knew that the deepest elephant sounds we hear, called grunts or rumbles, were merely the mild overtones of sounds so low and powerful they travel unhampered for miles through Asian forest. African elephants use similar signals.

Elephants live in layered societies, and like any social animal must communicate. These largest of land animals communicate with every sense: touch, taste, smell, vision and hearing. All work at close range, within a small band of elephants browsing together, or between mother and calf, or mating male and female, for example. With their long trunks, elephants can keep track of odors on the ground as they walk head up, and they routinely touch and smell each others’ bodies with their trunks.

But it was their sense of hearing that baffled early naturalists and makes long-distance communication—and therefore elephant society and mating—possible. Small groups of related adult females and their young of both sexes form the basic unit in elephant society, called a family. Females remain in families for life. The family often contains three generations, and may remain stable for decades or even centuries. Families associate with one to five other families, probably consisting of more distant relatives. These so-called bond groups in turn belong to larger groups, called clans.

William Langbauer, of the Pittsburgh Zoo, and several colleagues, including Charif, have characterized several specific infrasonic calls based on when they occur and how elephants hearing these calls react. Elephants appear to produce their extremely low-pitched sounds with a larynx similar to those of all mammals, but much larger.

When individual family members reunite after being separated, they greet each other enthusiastically, and the excitement increases with the length of time separated. They trumpet, scream and touch each other. They also use a greeting rumble, which begins at a low 18 Hz, crests at 25 Hz—just audible to humans—and falls back to 18Hz. An elephant attempting to locate its family uses the contact call, a relatively quiet low tone with a strong overtone audible to humans. Immediately after contact calling, the elephant will lift and spread its ears and rotate its head, as if listening for the response. The contact answer is louder and more abrupt than the greeting call, trailing off at the end. Contact calls and answers may continue for hours until the elephant successfully rejoins her family. At the end of a meal, when it’s time to move on, one member of a family moves to the edge of the group, typically lifts one leg and flaps her ears. She repeats a “let’s go” rumble, which eventually rouses the whole family, who then hit the road.

Unlike the highly social females, males leave their families at about 14 years of age. They travel alone or congregate in small loose groups with other males, occasionally joining a family on a temporary basis. When males come into musth, they wander widely, searching for receptive females.

Females typically come into estrus only once every four years, and then for only four days. So competition is intense, and males must have some way of finding mates from long distances. A male in musth repeats a distinctive set of calls called musth rumbles, listening for a response afterward. Males who hear this sound keep away, as bulls in musth are aggressive and dangerous. Females, however, answer with the so-called female chorus. This consists of several females answering with a call similar to the greeting rumble, but somewhat lower. Females will also give this call when a musth male joins their group or when they smell the strong urine of a musth male. A male homes in on the female chorus, hoping to find a female in estrus. After mating, the female rumbles out the post-copulatory sequence, a group of six grunts with strong overtones. She repeats this sequence several times, continuing for up to half an hour.

All of these calls serve as short-range communication in elephants. Documenting the effectiveness of long-range communication has proved technically difficult, however, even among radio-collared elephants. Despite the difficulties, says Charif, “Elephants may routinely know the whereabouts (and maybe activities) of other elephants that are several miles away from them. When a biologist in the field observes the behavior of a group of elephants, s/he may be missing a lot of subtle long-range interactions.”

A variety of theories have been proposed over the years to explain why sexual reproduction may be more advantageous than asexual reproduction, and, for that matter, why sexual reproduction even exists at all. For years everyone accepted the general proposition that sex is good for evolution because it creates genetic variety, which, in turn, is useful in adapting to constantly changing and challenging environments. But it may give organisms a very different kind of edge.
By the late 1980s, in the contest to explain sex, only two hypotheses remained in contention.

One, the deleterious mutation hypothesis, was the idea that sex exists to purge a species of damaging genetic mutations; Alexey Kondrashov, now at the National Center for Biotechnology Information, has been its principal champion. He argues that in an asexual population, every time a creature dies because of a mutation, that mutation dies with it. In a sexual population, some of the creatures born have lots of mutations and some have few. If the ones with lots of mutations die, then sex purges the species of mutations. Since most mutations are harmful, this gives sex a great advantage.

But why eliminate mutations in this way, rather than correcting more of them by better proofreading? Kondrashov has an ingenious explanation of why this makes sense: It may be cheaper to allow some mistakes through and remove them later. The cost of perfecting proofreading mechanisms escalates as you near perfection.

According to Kondrashov's calculations, the rate of deleterious mutations must exceed one per individual per generation if sex is to earn its keep eliminating them; if less than one, then his idea is in trouble. The evidence so far is that the deleterious mutation rate teeters on the edge: it is about one per individual per generation in most creatures. But even if the rate is high enough, all that proves is that sex can perhaps play a role in purging mutations. It does not explain why sex persists.

The main defect in Kondrashov's hypothesis is that it works too slowly. Pitted against a clone of asexual individuals, a sexual population must inevitably be driven extinct by the clone's greater productivity, unless the clone's genetic drawbacks can appear in time. Currently, a great deal of effort is going into the testing of this model by measuring the deleterious mutation rate, in a range of organisms from yeast to mouse. But the answer is still not entirely clear.

In the late 1980s the Red Queen hypothesis emerged, and it has been steadily gaining popularity. First coined by Leigh Van Valen of the University of Chicago, it refers to Lewis Carroll's Through the Looking Glass, in which the Red Queen tells Alice, "[I]t takes all the running you can do, to keep in the same place." This never-ending evolutionary cycle describes many natural interactions between hosts and disease, or between predators and prey: As species that live at each other's expense coevolve, they are engaged in a constant evolutionary struggle for a survival advantage. They need "all the running they can do" because the landscape around them is constantly changing.

The Red Queen hypothesis for sex is simple: Sex is needed to fight disease. Diseases specialize in breaking into cells, either to eat them, as fungi and bacteria do, or, like viruses, to subvert their genetic machinery for the purpose of making new viruses. To do that they use protein molecules that bind to other molecules on cell surfaces. The arms races between parasites and their hosts are all about these binding proteins. Parasites invent new keys; hosts change the locks. For if one lock is common in one generation, the key that fits it will spread like wildfire. So you can be sure that it is the very lock not to have a few generations later. According to the Red Queen hypothesis, sexual reproduction persists because it enables host species to evolve new genetic defenses against parasites that attempt to live off them.

Sexual species can call on a "library" of locks unavailable to asexual species. This library is defined by two terms: heterozygosity, when an organism carries two different forms of a gene, and polymorphism, when a population contains multiple forms of a gene. Both are lost when a lineage becomes inbred. What is the function of heterozygosity? In the case of sickle cell anemia, the sickle gene helps to defeat malaria. So where malaria is common, the heterozygotes (those with one normal gene and one sickle gene) are better off than the homozygotes (those with a pair of normal genes or sickle genes) who will suffer from malaria or anemia.

One of the main proponents of the Red Queen hypothesis was the late W. D. Hamilton. In the late 1970s, with the help of two colleagues from the University of Michigan, Hamilton built a computer model of sex and disease, a slice of artificial life. It began with an imaginary population of 200 creatures, some sexual and some asexual. Death was random. As expected, the sexual race quickly died out. In a game between sex and "asex," asex always wins -- other things being equal. That's because asexual reproduction is easier, and it's guaranteed to pass genes on to one's offspring.

Next they introduced several species of parasite, 200 of each, whose power depended on "virulence genes" matched by "resistance genes" in the hosts. The least resistant hosts and the least virulent parasites were killed in each generation. Now the asexual population no longer had an automatic advantage -- sex often won the game. It won most often if there were lots of genes that determined resistance and virulence in each creature.

In the model, as resistance genes that worked would become more common, then so too would the virulence genes. Then those resistance genes would grow rare again, followed by the virulence genes. As Hamilton put it, "antiparasite adaptations are in constant obsolescence." But in contrast to asexual species, the sexual species retain unfavored genes for future use. "The essence of sex in our theory," wrote Hamilton, "is that it stores genes that are currently bad but have promise for reuse. It continually tries them in combination, waiting for the time when the focus of disadvantage has moved elsewhere."

In the years since Hamilton's simulations, empirical support for his hypothesis has been growing. There is, first, the fact that asexuality is more common in species that are little troubled by disease: boom-and-bust microscopic creatures, arctic or high-altitude plants and insects. The best test of the Red Queen hypothesis, though, was a study by Curtis Lively and Robert Vrijenhoek, then of Rutgers University in New Jersey, of a little fish in Mexico called the topminnow.

The topminnow, which sometimes crossbreeds with another similar fish to produce an asexual hybrid, is under constant attack by a parasite, a worm that causes "black-spot disease." The researchers found that the asexually reproducing topminnows harbored many more black-spot worms than did those producing sexually. That fit the Red Queen hypothesis: The sexual topminnows could devise new defenses faster by recombination than the asexually producing ones.

It could well be that the deleterious mutation hypothesis and the Red Queen hypothesis are both true, and that sex serves both functions. Or that the deleterious mutation hypothesis may be true for long-lived things like mammals and trees, but not for short-lived things like insects, in which case there might well be need for both models to explain the whole pattern. Perpetually transient, life is a treadmill, not a ladder.