Abstract: Probes, preferably optical probes for the invasive measurement of blood parameters consist of a plurality of sensors (or at least one sensor and a stabilizing core, or at least one single sensor), (11,17), each of these sensors (11,17) having a diffusion zone with a selective membrane (15) and all together surrounded by a stabilizing sheath (18); this sheath (18) is to be fastened on the sensor(s) (11,17) by a glue (22). A method is described for manufacturing such probes. This method includes the steps of covering the selective membrane (15) by a hardenable and soluble cover material (21), in particular a silicate, then fastening said sheath (18) on the sensors (11,17) by glue (22)--which cannot reach the selective membranes (15) as they are just covered by the cover material (21)--and then dissolving said cover material (21). This method guarantees that the selective membranes (15) are free of glue (22) after the manufacturing process.