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Rh blood corpuscles. The sanitary recommendations then recommended by him against malaria were adopted by the Austrian government. Further, he made observations on the biology of the mosquito that carries these protozoa. Then he worked out a blood parasite of the lizard, and discovered a Rhizopod, Leydenia, in the ascites fluid of man.

His next step was to study the parasites of the human colon, which had been called Amœba coli. Schaudinn discovered that this really is two distinct species, one of which is harmless, while the other, Entamœba histolytica, he proved to be the cause of human bloody dysentery.

His following contributions were devoted to the study of blood parasites, so-called hgemosphoridia. His initial memoir upon this subject was one of his most important. He studied the three bloodparasites of the owl, known as Proteosoma, Halteridium and Hæmamœba, which he proved to be stages of one and the same life cycle and to be flagellates and not sporozoa. Here also may be mentioned his conclusion that the organisms of human malaria are also flagellates. In connection with this study he worked out the biology of the mosquito (Culex pipiens) that infects the owl, and its mode of transference of the parasites. In his investigation of Spirochæte ziemanni he made the important discovery that the two main forms of blood flagellates, Spirochæte and Trypanosoma, are not bacteria, but flagellates, a discovery that has wonderfully clarified our knowledge of blood diseases.

In 1904 Schaudinn left Rovigno to enter the National Sanitary Commission at Berlin. He was fully recognized as the foremost investigator of Protozoan diseases, and though he had never studied medicine he became its consultant authority in Germany. Unwisely the German government for a time placed hindrances to his free initiative, and forced him to undertake certain work outside of his proper field; he had no choice but to accept these conditions, for he was a poor man with a family to support. Principles of patriotism decided him to decline a call to the professorship of protozoology recently started by the British government for the investigation of tropical diseases. At this time Schaudinn corroborated the interesting discovery of Looss, that the round worm Ankylostomum infects the mammalian host not through the mouth, but by entering the skin then being transported by the blood current to the lung, and thence to the intestine.

Perhaps what is the most important medical discovery made by him was that of 1905, when he found in the secretions of syphilitic growths a parasitic flagellate that he named Spirochæte pallida. Long had physicians searched for the cause of this disease, one of the most widespread and terrible of human disorders, and it was the crowning act of Schaudinn's life to have found it.