Asclepios with his daughter Hygieia
Hippocrates of Cos or Hippokrates of Kos (Greek: Ἱπποκράτης; Hippokrátēs; ca. 460 BC – ca. 370 BC) was an ancient Greek physician of the Age of Pericles (Classical Athens), and is considered one of the most outstanding figures in the history of medicine. He is referred to as the father of Western 
medicine in recognition of his lasting contributions to the field as the founder of the Hippocratic School of medicine. This intellectual school revolutionized medicine in ancient Greece, establishing it as a discipline distinct from other fields that it had traditionally been associated with (notably theurgy and philosophy), thus establishing medicine as a profession.
However, the achievements of the writers of the Corpus, the practitioners of Hippocratic medicine, and the actions of Hippocrates himself are often commingled; thus very little is known about what Hippocrates actually thought, wrote, and did. There are also claims that point to Imhotep of ancient Egypt as history's first physician. Nevertheless, Hippocrates is commonly portrayed as the paragon of the ancient physician. In particular, he is credited with greatly advancing the systematic study of clinical medicine, summing up the medical knowledge of previous schools, and prescribing practices for physicians through the Hippocratic Corpus and other works.
Asklepieion on Kos Historians agree that Hippocrates was born around the year 460 BC on the Greek island of Kos (Cos), and became a famous ambassador for medicine against the strong opposing infrastructure of Greece. For this opposition he endured a twenty year prison sentence where he wrote very well known medical publications such as The Complicated Body, encompassing many of the things we know to be true today.
Soranus of Ephesus, a 2nd-century Greek gynecologist, was Hippocrates' first biographer and is the source of most information on Hippocrates' person. Information about Hippocrates can also be found in the writings of Aristotle, which date from the 4th century BC, in the Suda of the 10th century AD, and in the works of John Tzetzes, which date from the 12th century AD.
Soranus wrote that Hippocrates' father was Heraclides, a physician; his mother was Praxitela, daughter of Tizane. The two sons of Hippocrates, Thessalus and Draco, and his son-in-law, Polybus, were his students. According to Galen, a later physician, Polybus was Hippocrates' true successor, while Thessalus and Draco each had a son named Hippocrates.
Soranus said that Hippocrates learned medicine from his father and grandfather, and studied other subjects with Democritus and Gorgias. Hippocrates was probably trained at the asklepieion of Kos, and took lessons from the Thracian physician Herodicus of Selymbria. The only contemporaneous mention of Hippocrates is in Plato's dialogue Protagoras, where Plato describes Hippocrates as "Hippocrates of Kos, the Asclepiad." Hippocrates taught and practiced medicine throughout his life, traveling at least as far as Thessaly, Thrace, and the Sea of Marmara. He probably died in Larissa at the age of 83 or 90, though some accounts say he lived to be well over 100.
Hippocrates is credited with being the first person to believe that diseases were caused naturally and not as a result of superstition, and gods. Hippocrates was credited by the disciples of Pythagoras of allying philosophy and medicine. He separated the discipline of medicine from religion, believing and arguing that disease was not a punishment inflicted by the gods but rather the product of environmental factors, diet, and living habits. Indeed there is not a single mention of a mystical illness in the entirety of the Hippocratic Corpus.
Ancient Greek schools of medicine were split (into the Knidian and Koan) on how to deal with disease. The Knidian school of medicine focused on diagnosis. Medicine at the time of Hippocrates knew almost nothing of human anatomy and physiology because of the Greek taboo forbidding the dissection of humans. The Knidian school consequently failed to distinguish when one disease caused many possible series of symptoms. The Hippocratic school or Koan school achieved greater success by applying general diagnoses and passive treatments. Its focus was on patient care and prognosis, not diagnosis. It could effectively treat diseases and allowed for a great development in clinical practice.
Source and References http://en.wikipedia.org/wiki/Hippocrates_of_Cos