Alexander Monro Secundus
Alexander Monro of Craiglockhart and Cockburn was a Scottish anatomist, physician and medical educator. He is typically known as Alexander Monro secundus to distinguish him as the second of three generations of physicians of the same name. His students included the naval physician and abolitionist Thomas Trotter. Monro was from the distinguished Monro of Auchenbowie family. His major achievements included, describing the lymphatic system, providing the most detailed elucidation of the musculo-skeletal system to date and introducing clinical medicine into the curriculum. He is known for the Monro–Kellie doctrine on intracranial pressure, a hypothesis developed by Monro and his former pupil George Kellie, who worked as a surgeon in the port of Leith.
Alexander Monro, the third and youngest son of Isabella Macdonald of Sleat, and Alexander Monro primus was born at Edinburgh on 20 May 1733. He was sent with his brothers to Mr Mundell's school, where he learned the rudiments of Latin and Greek, and showed early evidences of great ability. Among his school-fellows were Ilay Campbell who was afterwards Lord President of the Court of Session and William Ramsay of Barnton, the banker. Monro's father decided to make him his successor and sent him to the University of Edinburgh when he was 12 years old, to attend the ordinary course of philosophy before beginning his professional training. He studied mathematics under Colin Maclaurin and ethics under Sir John Pringle. He was also a favourite of Matthew Stewart, Professor of Experimental Philosophy. He showed an interest for anatomy and after entering on the medical course, aged 18, he became a useful assistant to his father in the dissecting room. He attended the lectures of Drs Rutherford, Andrew Plummer, Alston and Sinclair. He possessed an insatiable thirst for medical knowledge, an uncommon share of perseverance, and a good memory.
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In 1771, he wrote a paper on the effect of drugs on the nervous system. He published two controversial observations on the lymphatics in 1758, maintaining that he—in De Venis Lymphaticis Valvulosis, a short essay printed at Berlin in 1758 and reprinted in 1761 and 1770—had first correctly described the general communications of the lymphatic system. William Hunter disputed this vigorously before they both realized Francis Glisson had published on the topic a century before, to insufficient general notice. The German Friedrich Hoffmann is now sometimes credited for preceding all three. In 1783, he published in Edinburgh Observations on the Structure and Functions of the Nervous System, dedicated to the Right Hon. Henry Dundas, and it is in consequence of the description in this book of the communication between the lateral ventricles of the brain that his name is known to every student of medicine at the present day. The opening now always spoken of as the "foramen of Monro" is very small in the healthy brain, but when abnormal accumulation of CSF on the brain is present (known as hydrocephalus) may be as wide as 20 mm. It was this morbid condition that drew Monro's attention to the foramen, and he first described it in a paper read before the Philosophical Society of Edinburgh in 1764, but gives a fuller account in this work on the nervous system. A further important observation in this paper was that the healthy cranial cavity is rigid and of constant volume and, he argued, that since the brain "is nearly incompressible, the quantity of blood within the head must remain the same." This was taken up by his former student George Kellie who set out the hypothesis that the contents of the skull (blood, CSF, and brain tissue) are a state of volume equilibrium, so that any increase in volume of one of the cranial constituents must be compensated by a decrease in volume of another. This has since been validated and is known as the Monro–Kellie doctrine.
