The bottom of the cuvette comprises a curved raceway placed so as to guide the oscillating movement of a ball inserted into the cuvette. In addition, the cuvette comprises means of attachment, in two perpendicular directions, to adjacent unit cuvettes. The cuvettes can thus be stored as plates in a feed magazine of an analytical device. The analytical device comprises several stations placed around a rotary ring. Only where it is desired to determine the clotting time of the blood contained in the cuvette a ball is introduced into the latter, at a ball distribution post. The cuvette equipped in this way is then brought to a station where the test is carried out. The major advantage of the invention is the polyvalence of the cuvette and of the analytical device.