involution

(in-vo-lu’shun) [L. involu’tio; in into + vol’vere to roll]. 1. A rolling or turning inward. 2. The return of the uterus to its normal size after parturition. 3. A retrograde change: the reverse of evolution. i.-forms, forms of microdérganisms that have become degenerated from unfavorable surroundings. senile i., the shriveling of “an organ in aged people.