It is difficult to understand how Galen missed the circulation of the blood.  He knew that the valves of the heart determined the direction of the blood that entered and left the organ, but he did not appreciate that it was a pump for distributing the blood, regarding it rather as a fireplace from which the innate heat of the body was derived.  He knew that the pulsatile force was resident in the walls of the heart and in the arteries, and he knew that the expansion, or diastole, drew blood into its cavities, and that the systole forced blood out.  Apparently his view was that there was a sort of ebb and flow in both systems—­and yet, he uses language just such as we would, speaking of the venous system as “. . . a conduit full of blood with a multitude of canals large and small running out from it and distributing blood to all parts of the body.”  He compares the mode of nutrition to irrigating canals and gardens, with a wonderful dispensation by nature that they should “neither lack a sufficient quantity of blood for absorption nor be overloaded at any time with excessive supply.”  The function of respiration was the introduction of the pneuma, the spirits which passed from the lungs to the heart through the pulmonary vessels.  Galen went a good deal beyond the idea of Aristotle, reaching our modern conception that the function is to maintain the animal heat, and that the smoky matters derived from combustion of the blood are discharged by expiration.

I have dwelt on these points in Galen’s physiology, as they are fundamental in the history of the circulation; and they are sufficient to illustrate his position.  Among his other brilliant experiments were the demonstration of the function of the laryngeal nerves, of the motor and sensory functions of the spinal nerve roots, of the effect of transverse incision of the spinal cord, and of the effect of hemisection.  Altogether there is no ancient physician in whose writings are contained so many indications of modern methods of research.

Galen’s views of disease in general are those of Hippocrates, but he introduces many refinements and subdivisions according to the predominance of the four humors, the harmonious combination of which means health, or eucrasia, while their perversion or improper combination leads to dyscrasia, or ill health.  In treatment he had not the simplicity of Hippocrates:  he had great faith in drugs and collected plants from all parts of the known world, for the sale of which he is said to have had a shop in the neighborhood of the Forum.  As I mentioned, he was an eclectic, held himself aloof from the various schools of the day, calling no man master save Hippocrates.  He might be called a rational empiricist.  He made war on the theoretical practitioners of the day, particularly the Methodists, who, like some of their modern followers, held that their business was with the disease and not with the conditions out of which it arose.