Next to the occurrence of the liquefaction, the most important fact, in our judgment, is the frequent change of volume which the mass undergoes while liquid. We say while liquid, for we do not discover, either in the diary or in our researches elsewhere, any indication of such a change taking place while the blood is in its solid condition. But, while liquid, such changes are so frequent and so great that the diary, as we saw, noticed their absence or _quasi_-absence, during one octave, as something remarkable. The blood is said to be at its ordinary or normal level when it fills about four-fifths of the space in the ampulla, or vial. It has been known to sink below this, but very rarely. Ordinarily it is oscillating in volume, sometimes reaching the neck, or entering it so high as to leave only a thread of light, or even filling the neck up to where it enters the mass of soldering. The extreme distance between the two levels is about an inch and a half, and the volume must increase over twenty per cent. in order to rise from the ordinary level so as to fill completely the ampulla. The days are comparatively rare when some change of volume is not seen, either by increase or by decrease. The change is generally gradual, yet such as may be watched and followed. Sometimes, however, it is quite rapid in the ascent or the descent, or in its alternations of rising and falling; sometimes almost instantaneous--_in un colpo, in un tratto_. These ordinary oscillations or changes of volume, which occur at any time, may be looked on as the usual and minor form of one general and striking trait or mode of action. When the increase is carried to its utmost extent, the vial is seen to be completely filled; and this fulness, in turn, presents many variations to be studied. We may divide them into two classes. The first embraces all those cases in which the fulness terminates, and the blood commences to diminish in volume, at any time before the close of the octave; we may call these completed periods. The second embraces all those in which the fulness continues to the end, so that, on the last day of the octave, the blood is replaced in its closet still completely filling the ampulla; these we call incomplete periods.