52 Wager and Peniston.—Cytological Observations on 
in some cases it may be somewhat contorted. Some of the refractive 
granules in the cytoplasm are stained black, the others are very conspicuous, 
as is also the granule in the vacuole. The latter is commonly found towards 
one side of the vacuole, and is sometimes lodged in a fold ; occasionally 
threads connecting it with the side of the vacuole show clearly. In some 
cells the vacuole is not very clear ; in a few cases it is invisible, but 
a number of slightly refringent granules, which are obviously not the 
refractive granules seen in the living condition, can be seen in the position 
usually occupied by the vacuole; these sometimes show indications of 
a reticular arrangement. 
4. Perenyi s fluid. In from 5-15 minutes the nucleolus is clearly 
defined in intimate connexion with the vacuole, which remains clear, although 
somewhat contorted (Figs. 35,36). The nucleolus then tends to become less 
visible. When thoroughly fixed, the cells are smaller than in the living 
condition, and the granular contents are accentuated, although the refringent 
granules appear individually smaller ; the most conspicuous object in the 
cell is the granule in the centre of the vacuole. The nucleolus is difficult 
to distinguish ; it is visible as a lighter area in the cytoplasm and looks very 
much like an extension of the vacuole. The latter is smaller, but not con¬ 
torted, and is rarely sharply outlined. In many cells the vacuole is 
represented by a slightly paler area in the cytoplasm surrounded by slightly 
refringent granules. 
5. Corrosive Sublimate, (a) Concentrated solution in 5 per cent, acetic 
acid alcohol (70 per cent.) (Figs. 39-41). The cytoplasm becomes granular, 
obscuring the refringent granules. The nucleolus is defined as a paler 
area in the cytoplasm closely connected with the vacuole ; the latter shows 
clearly in contrast to the granular cytoplasm ; it is not contracted, but does 
not exhibit that peculiarly definite outline associated with iodine fixation. 
The refringent granule in the centre of the vacuole is conspicuous, (b) Con¬ 
centrated aqueous solution (Figs. 37, 38). The nucleolus is invisible ; the 
cytoplasm is homogeneous as in the living cell, but more refractive. The 
vacuole is clearly defined, but somewhat smaller than in the living cell, and 
is not contorted. The refractive granules are not so conspicuous as in the 
living cell, but are distinctly visible. Cells placed in this solution strongly 
resemble those that have been 5-10 minutes in Pasteur’s solution. 
6. Picric Acid. ( a ) Concentrated solution in 70 per cent, alcohol 
(Figs. 50-2). The granular contents of the cell are strongly accentuated ; 
the nucleolus and the refringent granules, with the exception of the large 
central one, are completely obscured by the dense, granular cytoplasm. 
The vacuole is practically invisible in most of the cells, although in some 
it is indicated as a less granular area irregularly outlined, sometimes 
associated with a similar smaller oval area corresponding to the nucleolus 
(Figs. 50, 51). The only clearly differentiated object in the cell is the large 
