CELLS LINING THE PERITONEAL CAVITY 413 
times found at about this time, but was always most irregular 
and never so sharp and characteristic as seen with trypan blue. 
The area of the cell just over the nucleus, which contained the lo- 
calized mass of dye, was humped up often to a considerable 
extent. When the staining was carried to the maximum used 
in these experiments, the edges of the supranuclear mass extended 
irregularly around the nucleus and reached the infranuclear 
zone, in this way forming a perinuclear belt, similar to, but much 
more extensive than, those found in the cells of the general 
serosal mesothelium. The cells had by this stage increased 
considerably in size and over a larger surface than at the stage 
when there was only a supranuclear swelling. In some few 
cells the mass of dye seemed to be around the pole of the nu- 
cleus, probably the first-formed area was somewhat displaced 
from the region of the center of the cell. This cap formation 
around the longitudinal pole of the nucleus was not as common 
as with trypan blue. The principal difference observed in the 
reactions of the cells to the two types of dyes was the greater 
tendency of the carmine to enter the supranuclear zone and to 
remain circumscribed, while the trypan blue extended towards 
the periphery and usually towards the infranuclear zone. In 
general the cells covering the spleen contained considerably 
more dye than any other serosal cells at the same general stage 
of staining. 
It has been reported elsewhere (Cunningham, ’21, ’22) that, 
in cats in which the splenic mesothelial cells had been irritated, 
the trypan blue granules tended to collect in the infranuclear 
zone of the cell together with many highly refractive droplets 
which were developed during the progress of the irritation. 
Further, it was found that in experimental hydremia in cats 
the fluid always collected in the infranuclear zone. The normal 
vital staining in the cat likewise tends towards the perinuclear 
rosette, but with a considerably greater tendency to the infranu- 
clear extension. Whether these differences are very important 
cannot be stated as yet, sufficient data on long-continued irrita- 
tions of the serosa of heavily stained rabbits not being com- 
pleted. The area which shows the most active vital staining 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 30, NO. 4 
