An account given of the lives of five great naturalists (Hippocrates, Aristotle, Galen, Vesalius and Harvey) will not be found devoid of interest. The work of each one of them marked a definite advance in the science of Biology. There is often among students of anatomy and physiology a tendency to imagine that the facts with which they are now being made familiar have all been established by recent observation and experiment. But even the slight knowledge of the history of Biology, which may be obtained from a perusal of this little book, will show that, so far from such being the case, this branch of science is of venerable antiquity. And, further, if in the place of this misconception a desire is aroused in the reader for a fuller acquaintance with the writings of the early anatomists the chief aim of the author will have been fulfilled.