A gas chromatograph with multiple valves is disclosed. A potential communication channel that traverses a subset of the nodes in the network is identified. vaults, of storage members, each vault containing approximately 100 individual cartridges, which each contain packages of unit-of-use doses of a given medication or other medical supply, such as syringes. The engagement element can then enter into engagement with the bar when the holder forms different angles with the latter and constitutes a support for the holder which retains the latter in an angular position occupied relative to the bar. The protection means comprise several add-on sectors assembled around the portion of the tube, each add-on sector being provided with an associated inner stiffener penetrating into the portion of the production tube through at least one through orifice, at least one of the add-on sectors being provided with at least one opening extending through the sector and its associated inner stiffener. The \u03b2-phenylethylidenehydrazine derivatives according to the invention generally correspond to the general formula:.