1. A cellular access system comprising: a sensor for placing multiple electrodes in close proximity to living cells below a tissue surface of a patient, the sensor comprising: a base having a top surface and a bottom surface; a plurality of projections extending from the bottom surface of the base, one or more of the projections including at least one electrode along its length; a signal connector linked with the at least one electrode for providing an electrical connection to the electrode; and a protective cap configured to protect one or more of the projections; wherein a pattern of the projections in the base defines a periphery, and the base comprises a flange portion extending radially outward from at least a portion of the periphery, and wherein the protective cap is configured to engage the flange portion, further comprising a tunneling device for passing the sensor under the skin of the patient, a flexible sheath which is placed under the skin after which the sensor is passed therethrough, wherein the flexible sheath comprises a separator for dividing the sheath into a pair of peelable sheath portions.