2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/122906We show that Jacobi's bound for the order of a system of ordinary differential equations stands in the case of a diffiety defined by a quasi-regular system. We extend the result when there are less equations than variables and characterize the case when the bound is reached.6 pages, submitted to the CRAS de ParisDifferential Geometry34A34; 34A26; 58A20text