|Emil von Behring, Shibasaburō Kitasato immunology|
Diphtheria bacilli and tetanus bacilli produce toxins To protect themselves infected animals produce antitoxins Emil von Behring and Shibasaburō Kitasato identified these antitoxins and showed that trans- ferring them to another animal conferred immunity.
That transferring serum from the blood of a horse infected with diphtheria conferred immunity to diphtheria in human beings supported the theory that fighting disease is the work of liquids in the blood not of its cells and had little to do with the four humors of ancient medicine or maintaining a healthy balance of humors by bleeding, cupping, emetics, or purges.
Blood, black bile, phlegm, and yellow bile, according to the ancients, mediate between the pure soul and the impure body, which, if it were balanced, would be sure, but I would rather a less messy cure, a fresh breeze, a light rain, the smell of a violet, or a kiss on the cheek.
Serum is the liquid in blood that rises to the top of a test tube when left overnight, leaving blood cells and clotting proteins settled at the bottom. Paraclete is a word from the Greek for the Holy Spirit, but more generally means mediator or advocate.
Humoral theory is now discredited; cells produce antitoxins and perform other tasks in protecting animals from disease. Serum therapy was used to successfully fight diphtheria and tetanus, and Kitasato later developed an antitoxin for anthrax, but if you search for serum therapy today in wikipedia you get the article on vaccination.
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