Rudimentary

RUDIMENTARY (from Latin rudimentum - rudiment), the original meaning - rudimentary, later meaning - underdeveloped, disappearing, residual. The term is used to denote the condition of an organ or part that has lost its significance during its historical development and is consequently on the path to disappearance. Since the structure of an organ does not always allow one to determine whether it is developing progressively or, conversely, is being reduced, and since we can never assert that any organ or part does not perform any function whatsoever, the establishment of the rudimentary condition of an organ is possible only by comparing it with the condition of a homologous organ or part in various related organisms, with the morphological criterion of rudimentary condition being insignificant size and simplified structure, and the physiological criterion being the absence or insignificance of that basic function which is characteristic of this organ (see examples under Rudimentary organs). The conventionality of the concept 'rudimentary' is revealed by such an example: the epiphysis (pineal gland) is a very important organ of internal secretion and as such cannot in any case be considered a rudimentary formation, however comparative-anatomical data show that in its origin it is an eye rudiment that has lost its function, which had in the most ancient vertebrates a very complex structure (with a retina, light-refracting body, etc.). In French and English embryological literature, 'rudimentaire', 'rudimentary' is understood as rudimentary in the original sense, i.e., as developing. However, sometimes in English and especially American literature this understanding is extended to phylogenetically developing organs, i.e., the term is used in a sense opposite to the generally accepted one.