Galen believed in the doctrine of the four elements, and his speculations led him into a belief in a further subdivision. "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." He held that there were three principles in man--spirits, solids, and humours--and eight temperaments ranging between health and disease and compatible with life. He retained a good deal of the teaching of the Pneumatic school, and believed that the pneuma was different from the soul, but the vehicle for the interaction of soul and body. From his theory of the action of the air through the nose on the contents of the ventricles of the brain is explained his use of sternutatories, and his belief in the efficacy of sneezing. Galen's classification of inflammations shows that his pathology was not nearly so accurate as his anatomy and physiology. He described (a) simple inflammation caused by excess of blood alone; (b) inflammation the result of excess of both pneuma and blood; (c) erysipelatous inflammation when yellow bile gains admission, and (d) scirrhous or cancerous when phlegm is present. He did good service by dividing the causes of disease into remote and proximate, the former subdivided into two classes--predisposing and exciting.