Lydia MI. Dewitt 205
which divide and redivide, the secondary branches often com-
municating by means of capillaries. Since Fig. 4 represents a
section only 5su in thick-
ness, some idea of the ra-
pidity of the branching and
the centralization of the
larger branches may be
gained, although a thicker z g
section would show greater e
continuity of the vessels. e
In sections stained with
hæmatoxylin and eosin, the
endothelial walls of the
blood-vessels seem to rest
directly upon the cords of
epithelial cells constituting }
the island, and in most
places no connective-tissue
capsule can be seen. Where
the area reaches the peri- - -
phery of the lobule as seen Fig. 4.-Section of area of Langerhans
in Fig. 3 and as is quite from pancreas of rat in which the veins
common, especially with the were filled with blcod The figure shows
the connection with the large vein and the
larger areas in the central arrangement of the sinusoids within the
portion of the pancreas, island as seen in a thin section. X 20oo.
loose connective tissue
forms its boundary and occasionally nucleated connective tissue
may be seen in other places separating the area from the acini.
In sections stained with Mallory's connective-tissue stain, a
delicate blue line is seen separating most of the cells; a thin,
but nearly if not quite complete, capsule of connective tissue
surrounds the area and sends in still more delicate sheaths for
the blood-vessels.
In the rabbit, I have found on an average about one area for each square
millimeter of section. As the average size of areas measured was .0oo34
c. mm., about T??85 of the pancreas was insular tissue. The measurements taken
were as follows'