Friday 9 August 2013

Leonardo and modern anatomy

I was hoping that we had passed beyond the "brownie-point" accounts of Leonardo's anatomical studies; that is to say valuing his work in terms of how far he was correct in terms of our present knowledge.

The item on Leonardo's anatomical drawings on the Today programme on BBC radio 4 was cast entirely in terms of how "modern" Leonardo's anatomies are.  Once this has been accepted as the framework for judgements, the inevitable question follows. "What did Leonardo contribute to modern medicine?"  "Ah.... actually nothing, since his work was not published, but it would have been the greatest had it been". Not direct quotes, but basically what was said. We can do better than this.

We are told, for instance, that Leonardo's use of sections anticipated CT and fMFRI scans. He did produce one early image of a leg cut into chunks like gigot chops, but the series of successive, very fine layers in modern scanning techniques actually grow of of 19th-century techniques of sectional anatomy presented on card or paper as extensive series of parallel slices. Leonardos use of sections (favouring solid over  pure sections) can best be understood in terms of his use of innovatory use of sections in architectural studies and engineering  - the sectioned dome of the human skull as the the sectioned dome of a temple -  and his quest for three-dimensional visualizations that would present a total picture of the forms and functions of the body as a microcosm or  "lesser world".

Leonardo's anatomies were not designed to perform the same function as the legions of sober illustrations in Henry Gray's Anatomy, Descriptive and Surgical. Leonardo's representations, like those in the great anatomical picture books that followed, were elaborate exercises in natural philosophy, displaying the magnificence of god's supreme creation, and the anatomist's mastery of it, rather than directly serving the standard needs of practicing physicians or even of operational surgeons.  The grand and lavishly illustrated books of anatomy, from Vesalius's Fabrica (1543) onwards were not text books for general medical training but were aimed at patrons and wealthy academic and medical elites. The levels of knowledge of internal structures and functions displayed by Leonardo and Vesalius could not for the most part be directly exploited by medical techniques in the 16th century. Their demonstrations of the "fabric" of the body were directed towards quite another end than medical practice.

It is of course of interest and relevance to Leonardo's own aspirations to see what he "got right" and what he "got wrong". We can better understand Leonardo's studies when we know what he was looking at and how his kind of looking and representation resulted in the drawings and notes that have survived. But if our modern judgements of rightness and wrongness steer the system of values though which he look at his drawings, we are misunderstanding both the magnificent totality of his vision (in and beyond anatomy) and the historical context in which it was vibrant.

A good example of how we may approach Leonardo through contemporary medical eyes without  asserting that such eyes present us with the way to understand his science is in Francis Well's recent book, The Heart of Leonardo. In my preface to his book I wrote that:

"Every drawing by Leonardo is simultaneously act of analysis as well as description. He cannot draw a form without intuitions about its function. To ascertain how a form works – with no deficiency or redundancy – he brings his knowledge of dynamics to bear on his accounts of structures in motion. He knows about weights, levers and pulleys, which he can apply to the functioning of the body. The skeleton and muscles serve as a compound machine, the mathematical trajectory of which enables humans to move their limbs with complete freedom in space – across what he calls a “continuous quality”. The complex motion of fluids, above all water, to which he devoted minute and exhaustive attention, becomes vital to his reading of the actions of the heart valves, which he shows to be miracles of geometrical engineering.  He cannot see what blood does in the valves, but he can transfer his knowledge of water vortices. He is a natural bio-engineer. Indeed, his plan to make a glass model of the neck of an aorta to test his notion of the internal currents of blood is entirely novel. He is determined to invent means to determine the “impetus” and “percussion” of the surging torrents of blood, even if he cannot see them first-hand within the heart.

"We do not have to validate Leonardo’s science in terms of contemporary knowledge, nor do we have to evaluate it by adducing its influence on the history of medicine. His visions of the human body and the body of the earth possess a beauty of insight that are uplifting in their own right, to no lesser degree than his works of art. And they stand as an enduring monument to an unconstrained quest for understanding across disciplines. However, it is thrilling to find that he can still conduct a creative dialogue with a major heart surgeon over the span of 500 years. Francis Wells brings his clinical eye to bear upon drawings we have long admired, and points out major features that we little understood and telling details that we had entirely missed.  He shows that no organ had ever been subjected to such remorseless visual enquiry and functional interrogation as Leonardo devoted to the heart."

 I am sorry that I mentioned bio-engineering. But most of if seems OK.


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