| Calcar avis | |
|---|---|
 Posterior and inferior cornua of left lateral ventricle exposed from the side. | |
 Coronal section through posterior cornua of lateral ventricle. | |
| Identifiers | |
| NeuroNames | 210 |
| TA98 | A14.1.09.285 |
| TA2 | 5660 |
| FMA | 83707 |
| Anatomical terms of neuroanatomy | |
Thecalcar avis,(calcarine spur) previously known as thehippocampus minor,[1] is an involution of the wall of thelateral ventricle'sposterior horn produced by thecalcarine fissure.[2]
It is sometimes visible onultrasound[3] and can resemble aclot.[4]
The ridge was originally described by anatomists as thecalcar avis, while the ridge running along the floor of thetemporal horn of the lateral ventricle was described by various names, in particular as thehippocampus. A classical allusion was introduced later with the termpes hippocampi, which may date back toDiemerbroeck in 1672, introducing a comparison with the shape of the folded back forelimbs and webbed feet of the Classicalhippocampus (Greek: ἱππόκαμπος), a sea monster with a horse's forequarters and a fish's tail. At a subsequent stage the hippocampus was described aspes hippocampi major, with the calcar avis being namedpes hippocampi minor.[5]
The renaming of the hippocampus as hippocampus major, and the calcar avis as hippocampus minor, has been attributed toFélix Vicq-d'Azyr systematising nomenclature of parts of the brain in 1786. While "hippocampus minor" was used interchangeably with "calcar avis" for much of the 19th century, for a few years after 1861 the former name was subjected to publicity and ridicule when the hippocampus minor became the centre of a dispute overhuman evolution betweenThomas Henry Huxley andRichard Owen, satirised as theGreat Hippocampus Question. The term hippocampus minor fell from use in anatomy textbooks, and was officially removed in theNomina Anatomica of 1895, but still featured in theEncyclopædia Britannica of 1926, and appeared in general dictionaries as late as 1957.[6]
This article incorporates text in thepublic domain frompage 831 of the 20th edition ofGray's Anatomy(1918)
