Alexander Monro secundus (1733-1817) was a Scottish physician and anatomist. Most notable contributions include works on the lymphatic system, the interventricular foramen (of Monro), and the Monro-Kellie doctrine
George Kellie (1770 – 1829) was a Scottish surgeon. Together with Alexander Monro secundus gave his name to the Monro-Kellie doctrine
The Monro-Kellie doctrine or hypothesis states that the sum of volumes of brain, cerebrospinal fluid (CSF) and intracerebral blood is constant. An increase in one should cause a reciprocal decrease in either one or both of the remaining two.