Although the basic principle of homeopathy, 'like cures like', was recognized by the ancient Greek physician Hippocrates of Kos during the Age of Pericles (ca. 460 BC – ca. 370 BC), it is the German physician Dr. Samuel Hahnemann who in the late 1700s is credited with its development as a viable medical practice. Disenchanted with what he saw as barbaric medical practices in the eighteenth century, Hahnemann came across 'A Treatise on Materia' by Dr. Edward Cullen in which Cullen stated that quinine was an effective treatment for malaria. Intrigued, Hahnemann investigated the effects of quinine on himself and his friends and found that, in a healthy person, quinine produced the same symptoms as the disease itself - fever, sweating and shivering - whereas in an ill person it appeared to act as a cure. Over a long period of time Hahnemann tested many different substances - animal, vegetable and mineral - on himself and noted down the symptoms produced, forming many “drug pictures.” To test his remedies on ill people he questioned his patients closely to build up a similar picture of their symptoms that he could then match to the relevant drug picture. He discovered that the closer the match, the more successful the treatment - like cures like, the first principle of homeopathy. He named this new method of healing “homeopathy” after the Greek words “homoeo”, meaning similar, and “pathy,” meaning suffering. Many substances that Hahnemann used were somewhat poisonous. To ensure their safety he developed a three-stage dilution and mixing process, called “succussion.” By repeated dilution and succussion, Hahnemann found that the more times a remedy had been diluted the faster and more effectively it worked. This process of dilution formed the second principle of homeopathy – “by extreme dilution the medicine's curative properties are enhanced and all the poisonous or undesirable side effects are lost.” During his research Hahnemann discovered that people varied in their responses to each remedy depending on their basic temperament. So homeopathy concentrates on treating the whole patient rather than the disease and this became the third principle of homeopathy.