The two most distinguished names are Herophilus--who, Pliny says, has the honor of being the first physician "who searched into the causes of disease"-- and Erasistratus.
Herophilus, ille anatomicorum coryphaeus, as Vesalius calls him, was a pupil of Praxagoras, and his name is still in everyday use by medical students, attached to the torcular Herophili.

Anatomy practically dates from these Alexandrines, who described the valves of the heart, the duodenum, and many of the important parts of the brain; they recognized the true significance of the nerves (which before their day had been confounded with the tendons), distinguished between motor and sensory nerves, and regarded the brain as the seat of the perceptive faculties and voluntary action.

Herophilus counted the pulse, using the water-clock for the purpose, and made many subtle analyses of its rate and rhythm; and, influenced by the musical theories of the period, he built up a rhythmical pulse lore which continued in medicine until recent times.

He was a skilful practitioner and to him is ascribed the statement that drugs are the hands of the gods.

There is a very modern flavor to his oft-quoted expression that the best physician was the man who was able to distinguish between the possible and the impossible.
Erasistratus elaborated the view of the pneuma, one form of which he believed came from the inspired air, and passed to the left side of the heart and to the arteries of the body.