220 Mforphology and P/ysiology of Areas of Laegerhans
ment of the areas from an epithèlial anlage also speaks against
the theory of the lymphatic structure. That they are not em-
bryonal remains may be readily seen from the fact that they
do not in any sense degenerate in adult life, but remain alive, with
a rich blood supply, and are, according to my experience, only
relatively larger and more numerous in the young than in the
adult. The rich blood supply, the absence of any appearance
of degeneration, and the occurrence of dividing cells, as noted
by Bizzozero and Vassale, by Schulze, and as I myself have
seen, all refute the theory that they are pancreatic acini under-
going regressive changes. These dividing cells were especially
numerous in the islands of the young child's pancreas, but some
cells undergoing division were seen in nearly every section stained
in Heidenhain's iron-lac-hæematoxylin. The theory that the
areas are being constantly derived from pancreatic acini and
changing again into the glandular tissue is based (I), on the in-
crease or diminution in the number and size of the areas during
different conditions of digestion, and (2), on the occurrence of
transitional forms, especially as shown by Lewaschew, after re-
peated pilocarpinization. Opie and Hansemann have repeated
Lewaschew's experiments with pilocarpin, making careful counts
of the islands, but have found no increase in the number of
islands and no transitional forms. Ssobolew tested hunger,
active digestion, and pilocarpin and found areas only slightly
altered in number.
There is no question that structures do appear at times which
might be interpreted as transitional forms. I have not infre-
quently seen groups of tubules in which the characteristic
differentiation into two zones was entirely absent, the nuclei
being centrally placed in the cells; these groups looked not unlike
large islands of Langerhans, especially if, as sometimes happens,
no lumen could be made out in the tubules. Sometimes, also,
the eosinophile cells of the areas may be so numerous and so
arranged as to resemble somewhat the tubules just mentioned.
In the guinea-pig, I have once or twice seen, in apparent con-
nection with one of the central areas, tubules having no outer
basophile zone and having the nuclei centrally placed. These,