“This doctrine of the supreme authority of the heart, as being the focus of heat, thus maintained by Aristotle, was eagerly defended by the great Arabian commentator, Averrhoes, and by his countryman, Avenzoar, who keenly attacked Galen for having questioned its truth, and taught, as they represent, that the brain is the leading organ in the animal frame. After having, however, carefully ransacked every part of Galen’s works, in which I could suppose it likely to meet with any allusion to this doctrine, I am led to believe that these Arabians, in the heat of controversy, have misrepresented the real opinion of their master’s rival. Galen appears decidedly to have maintained with Hippocrates—‘that there is in the body no one beginning, but that all parts are alike, beginning and end: for a circle has no beginning.’ Agreeably to this idea, Galen remarks, that the brain cannot properly be said to derive its powers from the heart, since an animal will run, breathe, and cry after its heart has been taken out; nor can the heart be said properly to derive its powers from the brain, since it will palpitate and contract, after all communication with the brain is cut off, nay, after it has been removed from the body. In so far, then, the functions of the brain and the heart are independent of one another. But the brain is dependent upon the heart and its appendages for vital heat, without which it would be unable to continue its functions; and the heart, on the other hand, is dependent upon the brain for imparting nervous influence to the respiratory organs, without which it could not preserve its vital heat unaltered. Hence the mutual connexion and sympathy of important organs—a doctrine much insisted upon by ancient authors, and which bears some resemblance to the theory lately advanced by Mr. Morgan and Dr. Addison. “We shall now have no difficulty in understanding the ideas of the ancients regarding the operation of opium. Galen and Avicenna believed that the poison exerts its primary influence upon the heart, and impairs its vital heat. Of course they considered its operation on the brain as secondary. They called the action of narcotics frigorific or congealing, no doubt because they remarked that it was attended with a diminution of vital heat, and to this they attributed the loss of sensibility and muscular energy. I leave it to the reader to judge whether this theory or the modification of it lately proposed by Messrs. Morgan and Addison be the more plausible.” (Edinburgh Medical and Surgical Journal, No. 103.)