Meckel on developmental pathology.

Abstract

Before Schleiden and Schwann, Darwin and Mendel there passed briefly a towering giant, Johann Friedrich Meckel the Younger (1781-1833), now glimpsed only fleetingly and obscurely through the mist of time and former controversies, who can nowadays easily and clearly be identified as the father of a "pre-modern" developmental biology. At his beginning this prodigiously gifted physician-scholar had, as one would say nowadays, an unfair advantage, his cradle having been rocked, as it were, by the preparators in his father's and grandfather's huge collection of normal and abnormal anatomical "specimens" in the home in which he was born and raised including his father's own skeleton (with two anatomical anomalies!). Initially reluctant to follow in the steps of his illustrious anatomist/physician grandfather and father, he nevertheless early demonstrated extraordinary gifts in anatomy and zootomy. Napoleon's conquest of his homeland notwithstanding, Meckel spent at least 2 extremely fruitful years in Paris, under the tutelage of Cuvier, but also in close contact with Geoffroy St. Hilaire (Etienne), Lamarck, and von Humboldt. He not only translated Cuvier's Leçons d'anatomie comparée into German but also greatly enriched this pivotal treatise with observations of embryonic and malformed fetuses and animals only of passing interest to his mentor. In his numerous publications, Meckel was the first to relate abnormal to normal development, define anomalies of incomplete differentiation (vestigia), but, most importantly, to relate those malformations known in humans to those that are normal adult developmental states in "lower" animals (atavisms). Thus, Meckel's three-fold parallelism of the scala naturae, normal ontogeny, and the malformations in humans and animals makes him a recapitulationist par excellence, however, without ever venturing into a fully articulated and explicit theory of descent. Today Meckel is remembered solely as the discoverer of the syndrome and cartilage named after him, and as having interpreted, correctly, the developmental nature of the "Meckel" diverticulum. It is virtually unknown that Meckel also first enuntiated the concept and distinction between primary and secondary malformations/anomalies, introduced the notion of heredity into the causal analysis of congenital anomalies, was the father of syndromology (the Meckel syndrome), had a clear understanding of pleiotropy and heterogeneity, and can unequivocally be regarded as the father of developmental pathology. In hindsight, and inspite of much professional success, Meckel emerges as a tragic figure in the history of biology, his life cut short at 52 without an ability to incorporate cell theory and the embryological insights of his younger contemporaries into his intellectual edifice which might have made it possible for him to finally and clearly see "analogy" (now homology), of which he was the greatest expert in his era, as incontrovertible evidence for descent. In that case, Darwin and Haeckel might have even had the courtesy of a tip-of-the-hat in Meckel's direction.