198 Morphology and Physiology ofAreas of Langerhans
stain, Weigert's elastic stain, and in some few cases in Heiden-
hain's iron-lac hæematoxylin and in saffranin and Licht-grun.
Some of the most satisfactory and instructive preparations
were those in which there was some congestion so that there
was a physiologic vascular injection. These were often more
satisfactory for study of the structure than those injected with
a gelatin mass, in which the cells of the areas were often more
or less changed. For the injected preparations, the simple
Berlin blue and carmine gelatin masses were used and also a
double injection, the veins being filled with the Berlin blue or
Carmine gelatin, while the arteries were filled with a granular
mass (cinnabar or ultra marine blue.) In this procedure it was
difficult to prevent a rupture of the smaller vessels and an ex-
travasation of the granular mass, but some areas of the pancreas
often showed a good double injection. In the estimation of the
size of the areas, sections near the center of the areas were
measured for the first two dimensions, while the third was
obtained by counting the number of sections of the series through
which the given area extended and multiplying by 50, the
thickness of the sections. It is easy in nearly all forms to dis-
tinguish the central from the peripheral sections, not only by
their size but also by the fact that in the center of each area
the smallest cords of cells and the largest blood-vessels are
found. The volume, as given, is never exact, since it is obtained
by simply multiplying the three dimensions, together. However,
it answers the purposes of comparision and any more exact
method would be exceedingly difficult because of the irregular
shapes of the areas.
In the guinea-pig, I found an average of I.07 areas per square millimeter or
I.I4 areas per cubic millimeter. As the average volume of these areas was
.oo09 cu. mm., about one hundredth of the pancreas consists of island tissue
The areas vary greatly in size and shape as may be seen from a comparison
of the measurements of the following ten areas-
I. 0.40 x 0.32 X 0.285 mm.................. 0.036 c. mm.
2. o.I3 x 0.30 x o.I2o m m........... . 0.0047 c. mm.
3. 0.29 x 0.33 x o.II5 mm............ O.O.I c. mm.
4. o.I4 x 0.45 x o.I85 mm. ...:............. 0.OI2 c. mm.
5. o.I5 x 0,32 X 0-I75 mm ........0....... o,oo98 c. mm.