50 A.D.: Pneumatic School of Medicine

About 50 A.D.  Athenaeus of Attaleia established the Pneumatic School of Medicine, which is an advancement of sorts of the Hippocratic belief in the four humors.  Members of this school were known as "pneumatists,"  (1, page 490, 2 page 110)  which means they believed health was maintained by the balance of the humors and pneuma,  which means "vital air."  Pneuman was basically inhaled by breathing, and circulated by the vessels of the body. (2, page 110)

Pneumatists believed disturbances in the four humors, or an excess or deficiency in any one, would disturb the pneuma of that person, and cause medical problems. They also believed that (2, page 112)

• Blood is formed in the liver from food
• Phlegm is secreted from the brain to other organs
• Yellow bile comes from the liver
• Black bile comes from the spleen
• The most important organ is the heart, since it's the site of heat and pneuma
• The heart draws pneuma from the lungs, which is stimulated by it
• The spinal cord was an expansion of the brain, so all neurons began in the brain
• Respirations are a result of expansion and contraction of the lungs, involving the thorax and diaphragm

Further reading:

1. 1st Century:  The four schools of medicine (4/23/13)
2. 100 A.D.:  Aretaeus defines asthma

References:

1. Moffat, John, translator, "Aretaeus: consisting of eight books, on the causes, symptoms, and cure of acute and chronic diseases; translated from the original Greek." 1785, London, Logographic Press
2. Magill, Frank N., editor, "Dictionary of World Biography," Volume I: The Ancient World, 1998, Salem Press Inc., California

Note to self:  If references are off, see post: 50 A.D.: Aerateus, first accurate description of asthma