The needle used should be matched to the vessel size and should preferably be of relatively large bore to facilitate rapid collection. Vacutainers may be used, provided that the vein does not collapse. The bleeding of rabbits through an ear vein should be performed with a needle rather than with a scalpel, because of the difficulties inherent in stopping bleeding of a cut vessel. Butterfly needles are recom- mended, as they allow the animal to move its head during the procedure.