Charcot identifies and illustrates amyotrophic lateral sclerosis.

Jean-Martin Charcot described what he called amyotrophic lateral sclerosis in his 12 ^th and 13 ^th lessons published in 1873 by Bourneville. He distinguished the symptoms that were related to the lesion of the anterior horn of the spinal cord and those that were due to the degeneration (that he named "sclerosis") of its lateral column. He thought that "inflammation" progressed from the lateral column to the anterior horn (but the term inflammation is not to be taken in the current meaning): the lesion of the anterior horn was thus "deuteropathic". An album containing drawings made by Charcot is kept in La Salpêtrière Neuropathology Department. Four drawings are pasted on one of its pages, showing the degeneration of the pyramidal tract. They constitute the original of the engravings illustrating Charcot's 12 ^th lesson. The illustration of the fascicular atrophy of the adductor pollicis presented in the album does not appear in the lessons, even though this alteration is widely discussed and linked to the lesion of the anterior horn, which was supposed to ensure the "nutrition" of the muscle. The technique used by Charcot and his interpretation of the microscopic pictures, as exposed in his lessons, are discussed.