History of Scarlet Fever : Werewolves, Sennert and Scarlet Fever

 I have previously talked about Johann Weyer, a prominent medic with an interest in witchcraft and magic. In the early renaissance, superstition still ruled, and there were a number of scholars  at the time who maintained an interest in the occult. Weyer was one of these. I've already talked about his work with respect to witchcraft, but I did not however talk about his work on Lycanthropy. That is, Werewolves.
The werewolf legend specifically refers to people who can turn into wolves on the full moon, or simply at will. These people were the undead, cursed individuals who roamed the earth to do the devil's work.
The Lycanthropic* legends can be found in various cultures and iterations, but it boils down to one thing: an individual who can, at will, turn into an animal.

During the witch hysteria of the middle ages, people in general were on high alert for supernatural activity of any sort. As well as women bieng convicted as witches, there were men who were tried as werewolves.
Weyer met with a number of them, including a man in Padua who could not be convinced that he wasn't a werewolf (Despite the threat of being burned alive). another man, a spaniard, held the belief that he could turn into a bear. Weyer's conclusion was that these people, like the witches he had previously encountered, were deluded, and should be put into asylums, as opposed to being executed.
 But Weyer didn't have the last word on this, and there were many who speculated on the source of this peculiar malady.
Ten years after Weyer made his observations on a scarlet fever outbreak, Daniel Sennert was born in the city of Breslau, at that time controlled by the Hapsburg's.
Sennert wrote extensively on topics ranging from medicine to science. It has been evinced by some that he came up with "corpuscular theory", which is the theory that all matter can be divided into small particles, which in turn could be subdivided into smaller ones and allow materials to change form. But at the same time, he also seemed to believe in the competing theory, atomism, in which the world is made of indivisible spheres of varying sizes that cannot be broken down.
Sennert, like Weyer , grew up in a superstitious atmosphere. Despite Weyer's many travails, werewolf and witch hysteria still permeated the public consciousness.
In one of Sennert's books , he writes of a mythical creature known as the Baslisk.
A basilisk is a strange creature that is born from athe egg of a rooster, or a hens egg hatched under a toad, depending on who you ask. It also looks different depending on who you decide is your source. However, what is shared in all of it's legends is how it kills ; a lethal gaze.
Sennert writes of an incident in Warsaw in 1587, where a basilisk was believed to be lurking in a cellar.  Two children and their nurse went into this cellar, and did not leave alive. The local inhabitants came up with an interesting solution to this situation.
They took a condemned criminal, and cut him a deal. He could go down into the cellar and face the basilisk, and should he survive, his sentence would be commuted.
He accepted, and was kitted out in protective coveralls, and a suit of mirrors, to ensure the basilisk's fatal gaze would be focused on it's own reflection, thus causing it to kill itself. The man descended into the cellar, and when he came out, he announced that the basilisk had been killed. He described a strange creature that had the "figure of a fowl, eyes and extra feet like a toad and highly coloured with spots".

Behold, the most terrifying Basilisk !

This account shows the fundamental differences between Sennert and Weyer, that become all the more startling when you look more closely. Sennert attended the University of Hittenberg  Wittenberg where he studied chemistry and medicine. But as he became more well regarded, he showed more credulity to the practice of magic. In contrast, Weyer was trained by a magician in the occult in his early years, and developed into a more sceptical physician.
Whilst Weyer's assessment of werewolves and witches was that they were mentally ill, Sennert took a different approach. Whilst he acknowledged in some cases that "natural Lycanthropy" can occur, which matches Weyer, he also believed in "Diabolical Lycanthropy"  which was caused by the Devil.
This was not to say that Sennert did not make any useful contributions to the science.
As a practical chemist, he performed many experiments which helped him formulate his opinions on corpuscularianism.
 Sennert also read a lot and widely about science, philosophy and alchemy, a fact that is reflected in his many writings. it is because of this that he was familiar with the work of Giovanni Fillippo Ingrassia. So when there was an disease outbreak in Wittenberg, he recognised the characteristic "Rubiolae" described by the eminent Sicilian.
  Sennert not only diagnosed these patients, but took it upon himself to study them as the disease developed.
He noticed that when scarlet fever subsides, the extensive skin rashes damage the skin and cause it to flake off. This characteristic "desquamation" had never been recorded before. But this was not all he found.
Recovering patients would also experience swelling in their joints and arthritis. He believed that there was a connection between these symptoms and the preceding scarlet fever. That these were "sequels" to scarlet fever.
This finding would still be controversial for nearly two hundred years afterwards. Part fo the reason for this is that these sequels did not necessarily occur immediately after the disease.
It is because of this that Sennert is not remembered for his belief in basilisks, or for his ideas on werewolves. He is remembered for what he got right about scarlet fever; not what he got wrong about the supernatural.

*despite the greek language roots, the word "Lycanthropy" can be used generally to describe any form of animal/man hybrid.

References:
 Books (accessible via Google Books)
Chapter 7 , History of Magic and Experimental Science Part 12 by Lynn Thorndike, reprint 2003

Anatomy of Melancholy Part 1 by Robert Burton 2002 reprint

Journals

Michael, E. (1997). Daniel Sennert On Matter and Form: At the Juncture of the Old and the New1 Early Science and Medicine, 2 (3), 272-299 DOI: 10.1163/157338297X00159

Rolleston, J. (1928). THE HISTORY OF SCARLET FEVER BMJ, 2 (3542), 926-929 DOI: 10.1136/bmj.2.3542.926