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arrangement of the secondary strands, similar to that described for the blood-
vessels of the bird. Such differences may be readily understood from a reference
to Plate XV, Fig. 2, if we imagine a section cutthrough the large sinusoids which
run nearly parallel to the plane of the section in that figure, we will have much
A
Fig. Is, A and B.-Sections of areas of Langerhans from pancreas of human
adult. A, near center of area; B, near periphery. X 200.
the appearance given in Fig. 9, A. If the section is cut in the same direction, but
between two layers of the larger sinusoids, we will get more the appearance given
in Fig. 9, B. In gençral, however, the strands of connective tissue in the human
areas, like the sinusoids of other forms, have a very irregular arrangement,
scarcely any two islands presenting exactly the same appearance.
A rather definite capsule of nucleated connective tissue surrounds most of the
areas. The only thing which is constantly noted, in the child as well as in the
adult, is that in the interior of the islands the strands of connective tissue as
well as the blood-vessels contained in them are larger and the masses of cells
smaller and more band-like, while the individual cells are generally larger than
at the periphery. This makes it easy, regardless of the size of the section, to
distinguish a central from a peripheral section. Fig. 5o may serve to illustrate
this point, A, of this figure, as well as A and B of Fig. 9; representing sections
from near the center of an area, while Fig. io, B, represents a section near the
periphery. The increase of connective tissue with age or with general sclerosis
of the gland and the very small amount in younger individuals and in animals
seem to indicate that the formation of the connective tissue within the islands
is secondary.