Louis Antoine Ranvier (1835-1922), French histologist.

Louis A. Ranvier was a French physician and pathologist working in the 19th century, famous for his discovery of myelin and the eponymous Nodes of Ranvier.  Although he also described other features of the nervous system, it is for these - miniscule gaps in the covering of nerve fibres - that he is best remembered.

Frenchmen, for some reason, are rarities when it comes to anatomical and aetiological eponyms. Compare, for example, with the german contingent  - Alzheimer, Brodmann, Creutzfeldt (and Jacob) Helmholtz, Lewy, Nissl, Wernicke…

We must therefore feel especially honoured for Ranvier's presence as figurehead of The Node.   

Ranvier, Louis-Antoine: a brief life history

SYLLABICATION: node of Ran·vier
PRONUNCIATION:   ränvy, rän-vy, rä-
NOUN: Inflected forms: pl. nodes of Ranvier

• 1835 Born in Lyons, France
• 1860 Was intern at the Paris hospitals;
• 1865 Completed his medical degree and went on to found a small private laboratory with Victor Cornil, where Medical students took courses in histology;
• 1875 Accepted Chair of General Anatomy at the Collège de France;
• 1878 Discovered myelin.  And nodes.
• 1897 Founded the 'Archives d'anatomie microscopique' with Balbiani;
• 1900 Entered retirement and moved to his estate in Thélys. 
• 1922 Died at Vendranges, France

Myelin and nodes

A Node of Ranvier is a constriction in the myelin sheath that encases nerve fibres, occurring at varying intervals along their length.  Following Louis' discovery, later researchers established that myelin was built up of the membrane of oligodendrocyte cells, wrapping themselves round the fibre to completely enclose it in multiple layers of fatty tissue. 

The essential feature of myelin is its high electrical insulation, as this prevents charged ions crossing the membrane of the fibre.  Ionic movements are restricted to the (aforementioned) nodes.  By limiting local circuits and causing the nerve impulse to 'jump' from one node to the next, the speed of conduction is increased many times over: from ~ 1.5 to 120 metres per second in mammals.

Multiple Sclerosis

In multiple sclerosis the myelin covering breaks down in regions of the CNS.   This greatly reduces the efficiency of nervous transmission and is thought to lead to the symptoms of MS - fatigue, muscle wasting, disrupted vision, loss of balance, and other problems.

Multiple sclerosis is an autoimmune disease; the immune system appears to lose its tight regulation and starts to attack the body's own cells.  Although it is a very active field of research, much remains to be learnt about its causes, development and treatment. 

Biography

1. Ranvier, Louis-Antoine und Victor André Cornil. 1869. Manuel d'histologie pathologique. Paris
2. Ranvier, Louis-Antoine. 1875-1882. Traité technique d'histologie. Paris
3. Ranvier, Louis-Antoine. 1878. Leçons sur l'histologie du système nerveux, par M. L. Ranvier, recueillies par M. Ed. Weber. Paris
4. Ranvier, Louis-Antoine. 1880. Leçons d'anatomie generale sur le système musculaire, par L. Ranvier, recueillies par M. J. Renaut. Paris
5. Ranvier, Louis-Antoine. 1885. Exposé des titres et des travaux de M. L. Ranvier. Paris