Abstract: An improvement to a functional module for the selective application of substances inside fertile eggs represents an inventive solution in the field of poultry fanning, in particular in the field of poultry breeding, and more specifically in the step of application of vaccines and/or nutrients into fertile eggs by injection, this improvement reducing the risk of violation of biological safety, and ensuring the integrity and survival of the embryo (Em), limiting intra-ovum nutritional supplementation to the amniotic fluid (Li) only, without contact of the needle (a13) with the embryo (Em), and to achieve this condition the module for the selective application of substances inside fertile eggs (Ov) has a structure composed of an injector selector submodule (m1), a selective operation actuation submodule (m2), a speed control submodule (m3) and a common perforator/needle return submodule (m4).