CELLS LINING THE PERITONEAL CAVITY 407 
Turning now to the reactions of this group of cells to intrave- 
nously administered carmine: in the early stages when the blue 
was found in a ring with a few scattered perinuclear granules 
the carmine was almost always in a small round or oval patch, 
always sharply localized in the cytoplasm. These carmine 
granules were almost always very small, uniform in size and 
evenly distributed. The regularity with which the early carmine 
staining showed this precise arrangement was quite remarkable. 
When the experimental animal had received more dye, ten to 
fourteen injections, the principal difference noted was the in- 
crease in the size of the patches of carmine granules and the 
beginning of the perinuclear rosettes. In animals in which 
the staining was carried much further—fifteen to thirty doses— 
the size of the isolated groups of dye-particles increased still 
more, and in many cases there were some granules which had 
apparently strayed away from the central fold so that these 
areas were no longer so sharply outlined. This distribution of 
the dye was particularly characteristic of the cells covering the 
diaphragm, the irregularity of the granules almost furnishing 
sufficient degree of difference to permit the classification of these 
cells in a separate group. These diaphragmatic mesothelial 
cells were the first to show perinuclear rosettes, though these 
were often most irregular and diffuse. Figure 8 shows two cells 
which were obtained from the surface of the diaphragm of a 
rabbit which had received twenty-five doses of carmine on alter- 
nate days; both the diffuse perinuclear arrangement and the 
irregularly scattered cytoplasmic granules are shown, but never- 
theless there is quite definite evidence of a greater concentra- 
tion of the dye in a definite part of the cell. Only in very rare 
instances have cells been found from any of the surfaces of the 
general serosa that did not present this wholly characteristic 
type of staining. 
In animals stained over a considerable length of time, surface- 
cells other than those of the diaphragm also contained more 
carmine granules, but distributed usually with greater regularity. 
In those over the stomach and intestine the additional granules 
were usually added to the preexisting small ring or mass, while 
