624 ; RECENT WORK ON INSULIN
produced.* This extract was also administered to a number of
normal rabbits. Characteristic insulin convulsions, which were
permanently alleviated by dextrose, were produced when the
dose was sufficient to cause marked hypoglycemia. A substance
which consistently produces all these effects possesses the essen-
tial and characteristic properties of insulin.
Scott, Smith and I (27) have reported in detail on the pres-
ence of insulin in practically all the tissues of the body. We
found insulin in the tissues of completely depancreatized dogs.
Some of these animals were in the end stages of diabetes when
they came to autopsy. Ashby (28) has been able to estract
insulin from various tissues. He was not able to demonstrate
any anitidiabetic substance in diabetic tissues. Several European
investigators have recently reported the presence of insulin in
various organs. Very recently Vincent (29) reports that Dodds
and Dickens have applied their revised method to the extraction
of insulin from ox submaxillary gland and that a yield of 2130
units per kilogram has been obtained. Vincent states that "the
fact that such large quantities can be prepared from a gland so
like the pancreas in general structure cannot be without some
fundamental significance. McAlpine in our laboratory has thus
far been unable to secure yields from this source comparable to
those reported by Vincent. MeAlpine has used the revised Dodds
and Dickens method. The significance of this active material
in tissues other than pancreas is not increased in proportion to
the absolute amount extracted by a certain method but depends
more upon (1) the demonstration that the substance is insulin,
and (2) the amount extracted by a given method compared to
the amount extracted from the pancreas by the same technique.
As we have reported elsewhere, thymus glands processed by our
present methods are a much more fruitful source of insulin than
pancreas extracted by the procedure originally used to prepare
insulin for clinical use. The fact that the pancreas is far richer
in insulin than any other tissue should not be overlooked.
There is still much to be learned concerning the distribution
of insulin in the body, but I believe that we should await devel-
opments in methods of preparation and especially of testing
* A weak insslin solution, as noted in the table. was administered per os to
this animal by mistake. A large amount of the potency w as recovered from the
arine. Numerous control experiments shiow that insulin per os does not affect the
b)lood sugar or liver glycogen.