Galen’s surgery is not of very great importance, but he is credited with the resection of a portion of the sternum for caries and with ligature of the temporal artery.[507] He applied the doctrine of the four elements to his theories of diseases. “Fire is hot and dry; air is hot and moist; for the air is like a vapour; water is cold and moist, and earth is cold and dry.” Galen’s pathology is explained by Sprengel thus: when the body is free from pain, and performs its functions without obstacle, it is in a state of health; when the functions are disturbed, there is a state of disease. The effect of disturbed functions is _the affection_ (πάθος); that which determines this injury is the cause of the disease, the sensible effects of which are the symptoms. Diseases (διάθεσις) are unnatural states either of the similar parts or of the organs themselves. Those of the similar parts proceed in general from the want of proportion among the elements, of which one or two predominate. In this manner arise eight different dyscrasies, or ill states of the constitution. Symptoms consist either in deranged function or vicious secretions. The internal causes of disease depend almost always on the superabundance or deterioration of the humours. Galen calls every disorder of the humours a putridity; it is due to a stagnant humour being exposed to a high temperature without evaporating. Thus suppuration and the sediment of urine are proofs of putridity. In every fever there is a kind of putridity which gives out an unnatural heat, which becomes the cause of fever, because the heart and the arterial system take part in it. Choulant enumerates eighty-three works of Galen which are acknowledged as genuine, nineteen which are doubtful, forty-five spurious, nineteen fragments; and fifteen commentaries on different books of Hippocrates; and more than fifty short pieces and fragments for the most part probably spurious, which are still lying unpublished in the libraries of Europe. Besides these Galen wrote many other works, the titles of which only remain to us; so that it is estimated that altogether the number of his different books cannot have been less than five hundred.[508] He wrote, not on medicine only, but on ethics, logic, grammar, and other philosophical subjects; he was therefore amongst the greatest and most voluminous authors that have ever lived.[509] His style is elegant, but he is given to prolixity, and he abounds in quotations from the Greek writers. PHILIP OF CÆSAREA was a contemporary of Galen about the middle of the second century after Christ. He belonged to the sect of the Empirici, and defended their doctrines. It is probable that he wrote on marasmus, on materia medica, and on catalepsy; but as there were other physicians of the same name, there is much uncertainty as to their identity.