Fluid injection port. An elastomeric injection nipple is supported within a compression fitting and the injection nipple includes a slit. A first via is provided that connects the slit in the nipple to a flow channel leading into a fluid reservoir. A venting channel is provided in fluid communication with the fluid reservoir and also in fluid communication with a second via. When a pipette is inserted into the slit in the injection nipple, the nipple deforms allowing the second via to be in fluid communication with space on either side of the pipette tip whereby air can be discharged.