236 Morphology and Ph/y.siology of Areas of Langerhans
complete; and(2) the insulæe in the cat's pancreas are generally
small and it is difficult to get, even from the larger omental
portion of the pancreas, when atrophied, sufficient extract to
make very many satisfactory tests. I feel sure, however, that
the chemical and physiological examination of isolated island
tissue offers the only certain means of deciding the difficult
questions regarding the function of these structures. While
my results must be regarded as relative rather than absolute,
they speak with no uncertain voice in favor of the theory that
the islands manufacture a substance, analogous to the "acti-
vator principle" described by Cohnheim, which favors the gly-
colytic action of muscle ferment. To make these results more
certain, it is necessary to use the isolated island tissue in large
enough amounts so that numerous tests may be made not only
of its activator action on muscle ferment, but also its effect on
blood pressure and, most important of all, its influence on the
experimental diabetes of depancreatized animals and on human
diabetics. It is a question whether the operative method can
in any animal furnish the isolated island tissue in large enough
amounts for these purposes.
Rehnie, however, has recently described two species of fish
(Lophius piscatorius and Scorpcena scropha) in which one large
"principal islet" and several smaller islands of structure analo-
gous to that of the areas of Langerhans in mammalia may be
distinguished with the unaided eye and may be dissected out
entirely free and isolated from pancreatic tissue. If these shall
prove to have the same function as the areas of Langerhans
in mammalia and other forms, they offer the opportunity for
further and more satisfactory investigation along these lines.
Since my experimental work was finished and had been reported
in part at the session of the Association of American Anatomists
at Philadelphia in I904, two preliminary reports have appeared,
one by Rennie himself and one by Diamare and Kuliabko,
announcing that they are now following out a similar line of
investigation on the isolated islands of these two species of fish.
The results given in their preliminary reports are by no means
decisive or very satisfactory. Rennie reports three tests, two