activity in the rodent LC was found in 1959, monoamines were found in 1964 and the widespread projections of noradrenergic neurons in the 1970s. An important advance in understanding the anatomical organization of the locus coeruleus was the application of the Falck-Hillarp technique, which combines freeze-dried tissue and formaldehyde to cause catecholamines (such as norepinephrine) and serotonin to fluoresce in tissue sections. Etymology Coeruleus or caeruleus The 'English' name locus coeruleus is actually a Latin expression consisting of the noun, locus, "place" or "spot" and the adjective coeruleus, "dark blue" or "sky-blue". This was aptly translated into English as blue place in 1907 in the English translation of the official Latin anatomic nomenclature of 1895, Nomina Anatomica. The name of the locus coeruleus is derived from its azure appearance in unstained brain tissue. The color is due to light scattering from neuromelanin in noradrenergic (producing norepinephrine) nerve cell bodies. The spelling coeruleus is actually considered incorrect, with dictionaries of classical Latin preferring caeruleus instead. Caeruleus is derived from caelum, hence the spelling with -ae, like caeluleus → caeruleus. Caelum in classical Latin could refer to the sky, the heaven or the vault of heaven. In mediaeval Latin, orthographic variants such as coelum for classical Latin caelum and cerulans for classical Latin caerulans can be found. In English, the color adjective cerulean is derived from Latin caeruleus. In addition, ceiling is ultimately derived from Latin caelum. Official Latin nomenclature The official Latin nomenclature, Nomina Anatomica as ratified in Basel in 1895 and in Jena in 1935 contained the orthographically correct form locus caeruleus. The Nomina Anatomica published in 1955 inadvertently introduced the incorrect spelling locus coeruleus, without further explanation. The subsequent edition monophthongized the diphthong, resulting in locus ceruleus, as they proclaimed that: "All diphthongs should be eliminated". This form was retained in the subsequent edition. The following two editions from 1977 and 1983 reverted the orthography back to the incorrect spelling locus coeruleus, while the subsequent edition from 1989 eventually returned to the correct spelling locus caeruleus. The current edition of the Nomina Anatomica, rebaptized as Terminologia Anatomica, dictates locus caeruleus in its list of Latin expressions and correspondingly mentions locus caeruleus in its list of English equivalents. This is in line with the statement made by the chairman of the Terminologia Anatomica that "the committee decided that Latin terms when used in English should be in correct Latin". See