Up to that time, those scientists who were synthesizing therapeutic agents came at their tasks with few hypotheses about where and how these agents interacted with living systems. Ehrlich supposed that living cells have side chains—a shorter chain or group of atoms attached to a principal chain in a molecule—much in the way that dye molecules were known to have side chains that were related to their coloring properties.
These side chains can link with particular toxins. According to Ehrlich, a cell under threat from foreign bodies grows more side chains, more than are necessary to lock in foreign bodies in its immediate vicinity. It was these antibodies, in search of toxins, that Ehrlich first described as magic bullets.
Serum therapy was for Ehrlich the ideal method of contending with infectious diseases. In those cases, however, in which effective sera could not be discovered, Ehrlich would turn to synthesizing new chemicals, informed by his theory that the effectiveness of a therapeutic agent depended on its side chains.
In Frankfurt, Ehrlich turned from his work on serum therapy to chemotherapies and dyes. First targeting the protozoa that were known to be responsible for certain diseases, such as sleeping sickness, he and the Japanese bacteriologist Kiyoshi Shiga synthesized trypan red as a highly effective cure for that disease. Soon this institute and the Hoechst and Cassella chemical companies reached an agreement that gave the companies the right to patent, manufacture, and market preparations discovered by Ehrlich and his colleagues.
The companies further agreed to supply chemical intermediates for the syntheses that the staff of the institute would undertake.
Salvarsan was used to treat syphilis until the s. The researchers, now including an organic chemist, Alfred Bertheim, and a bacteriologist, Sahashiro Hata, broadened the targeted microorganisms to include spirochetes, which had recently been identified as the cause of syphilis.
Salvarsan was first tried on rabbits that had been infected with syphilis and then on patients with the dementia associated with the final stages of the disease. More testing revealed that Salvarsan was actually more successful if administered during the early stages of the disease. Salvarsan and Neosalvarsan retained their role as the most effective drugs for treating syphilis until the advent of antibiotics in the s.
This work opened a way of obtaining numerous new organic compounds with trivalent arsenic which Ehrlich tested. At this time, the spirochaete that causes syphilis was discovered by Schaudinn and Hoffmann in Berlin, and Ehrlich decided to seek a drug that would be effective especially against this spirochaete. Among the arsenical drugs already tested for other purposes was one, the th of the series tested, which had been set aside in as being ineffective.
Hata did so and found that it was very effective. When hundreds of experiments had repeatedly proved its efficacy against syphilis, Ehrlich announced it under the name «Salvarsan». Subsequently, further work on this subject was done and eventually it turned out that the th arsenical substance to which the name «Neosalvarsan» was given, was, although its curative effect was less, more easily manufactured and, being more soluble, became more easily administered.
Ehrlich had, like so many other discoverers before him, to battle with much opposition before Salvarsan or Neosalvarsan were accepted for the treatment of human syphilis; but ultimately the practical experience prevailed and Ehrlich became famous as one of the main founders of chemotherapy. During the later years of his life, Ehrlich was concerned with experimental work on tumours and on his view that sarcoma may develop from carcinoma, also on his theory of athreptic immunity to cancer.
The indefatigable industry shown by Ehrlich throughout his life, his kindness and modesty, his lifelong habit of eating little and smoking incessantly 25 strong cigars a day, a box of which he frequently carried under one arm, his invariable insistence on the repeated proof by many experiments of the results he published, and the veneration and devotion shown to him by all his assistants have been vividly described by his former secretary, Martha Marquardt, whose biography of him has given us a detailed picture of his life in Frankfurt.
In Frankfurt the street in which his Institute was situated was named Paul Ehrlichstrasse after him, but later, when the Jewish persecution began, this name was removed because Ehrlich was a Jew. After the Second World War, however, when his birth-place, Strehlen, came under the jurisdiction of the Polish authorities, they renamed it Ehrlichstadt, in honour of its great son.
Olaf Order. In he shared with Metchnikoff the highest scientific distinction, the Nobel Prize. The Prussian Government elected him Privy Medical Counsel in , promoted him to a higher rank of this Counsel in and, in , raised him to the highest rank, Real Privy Counsel with the title of Excellency. Ehrlich married, in , Hedwig Pinkus, who was then aged They had two daughters, Stephanie Mrs. Ernst Schwerin and Marianne Mrs.
Edmund Landau. When the First World War broke out in he was much distressed by it and at Christmas of that year he had a slight stroke.
He recovered quickly from this, but his health which had never, apart from a tuberculous infection in early life which had made it necessary for him to spend two years in Egypt, failed him, now began to decline and when, in , he went to Bad Homburg for a holiday, he had, on August 20 of that year, a second stroke which ended his life. It was later edited and republished in Nobel Lectures. To cite this document, always state the source as shown above.
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