< Topic >Containment the animal for experiment where the mouse and the like is small relatively, easily the retention vessel for the mite which can get tattoo vis-a-vis lug mediating/helping is offered.SolutionsBeing the retention vessel containment the mite, as the barrel 2 which forms this retention vessel, has the plane surface 21a which parallels to the shaft center of this barrel 2 in the inner circumference, directs to the front and the inside of aforementioned barrel 2 does the reduction decrease, it features that lug mediating/helping of the suffering retention animal 5 which for retention state is, the job hole 25 of projection possible left and right pair is provided to outside.< Choice figure >Drawing 5【課題】マウスなどの比較的小さい実験用動物を保持し、容易に耳介に対して入墨することができる小動物用保定器を提供する。【解決手段】小動物を保持する保定器であって、この保定器を構成する筒体2が、この筒体2の軸心に沿った平面21aを内周に有し、前方に向けて前記筒体2の内面が縮減すると共に、保定状態にある被保定動物5の耳介を、外部へ突出可能な左右一対の作業孔25を備えたことを特徴とする。【選択図】図5