Robert Remak (1815-1865)

The autonomic nervous system and the origins of neurocardiology

Following new concepts by Bichat in the early 19th century, of organic and animal life centered around the ganglionic nervous system, over 100 years of anatomic studies and physiologic experimentation eventually resulted in Gaskell's 1916 book entitled "The Involuntary Nervous System" and Langley's 1921 book entitled "The Autonomic Nervous System." Neurology and cardiology emerged as specialties of medicine in the early 20th century. Although neurology made several prominent discoveries in neurophysiology during the first half of the 20th century, cardiology developed coronary care units and cardiac catheterization in the 1960s. Programmed electrical stimulation of the heart and noninvasive ambulatory monitoring provided new methodologies to study clinical cardiac arrhythmias. Experimentally, direct cardiac nerve stimulation of sympathetic nerve endings, as well as parasympathetic control of the atrioventricular node, provided the background to new detailed autonomic studies of the heart. Neurocardiology, perhaps initially more directed towards our understanding of sudden cardiac death, ultimately embraced an even significantly more complex scheme of local circuit neurons and near-endless loops of interconnecting neurons in the heart. Intrathoracic extracardiac and intracardiac ganglia have been recharacterized, both anatomically and physiologically, laying the groundwork for potential new therapies of cardiac neuromodulation.

The perversion of language: Jules Baillarger on aphasia, the lateralization of speech, and the Baillarger-Jackson principle

Jules Baillarger was one of the foremost figures of nineteenth-century neurobiology. He is remembered today for his discovery that the human cerebral cortex is composed of six intercalated layers. Even today, two horizontal fiber bundles within cortical layers IV and V are referred to as the outer and inner bands of Baillarger. It is a measure of the importance of Baillarger's discovery that his findings were elaborated upon with advances in microscopy and the development of methods for staining neurons and myelin by, notably, Theodor Meynert and Santiago Ramon y Cajal. Furthermore, Baillarger's observation that there are variations in the thickness of one or another of the six cortical layers in different cortical regions, and the discovery of giant pyramidal motor neurons in layer V of the precentral gyrus, ultimately led to the cytoarchitectonic and myeloarchitectonic maps of Oscar Vogt and Cécile Vogt-Mugnier, and of their student Korbinian Brodmann (1908). Less well known are Baillarger's contributions to the semiology of aphasia and the pivotal role he played in the recognition of the localization and lateralization of speech to the left hemisphere. Paul Broca's localization of articulate language to the posterior aspect of the frontal lobes and Marc Dax's discovery that speech is a function of the left hemisphere were vigorously challenged within French academic medicine until 1865, when Baillarger gave two addresses to the Royal Academy of Medicine. In the first address, he described a form of aphasia he called the perversion of language, which we now call fluent aphasia, and reported that aphasic patients can express words or parts of sentences when they are angry or excited, a phenomenon now known as the Baillarger-Jackson principle. In his second address, Baillarger supported the lateralization of speech to the left hemisphere of the brain and referred to this association as Dax's "singular law," and supported the localization of speech to the posterior aspect of the left inferior frontal gyrus. Baillarger's description of the perversion of language and of the influence of emotions on speech presaged the discipline of aphasiology, and his support for the lateralization of speech to the left hemisphere marks the first instance of the unequivocal recognition of asymmetrical hemispheric functions by academic medicine. This article reviews these aspects of Baillargher's career. Critical sections of his papers on cortical structure, aphasia, and functional hemispheric asymmetry are translated by the author.