These are only a very few examples from the long list of benefits
that have accrued to humanity through the use of living mammals for
experimental purposes. I must mention only one more――the recent
discovery of a specific treatment for diabetes. Less than two years ago
I invited a little girl to go for a bird walk with me that I might
give her the pleasure of stroking and feeding a wild bird in its nest.
I was particularly eager that she should enjoy that day, because both
she and I knew that she had not many days to live. She was doomed to
die of diabetes within six months; as a matter of fact she died in less
than three months from the date of our walk. I remember thinking that
I would give anything I possessed if I could by some miracle restore
that child to health. Today, less than two years later, that miracle
could be performed, because Dr. F. G. Banting of the University of
Toronto, by a brilliant series of experiments on dogs, has completed
investigations begun on rabbits by Claude Bernard seventy-five years
ago. The story of this wonderful discovery is long, but here are the
outstanding facts. It was found that when the pancreas of a dog is
removed, the animal at once develops acute diabetes and usually dies
of that disease within three or four weeks. Under the microscope the
pancreas is seen to be studded with countless little bodies, known as
the islands of Langerhans, after the German scientist who discovered
them. It was found that these islands secrete a substance quite
different from that secreted by the rest of the pancreas, and that
it is the absence of this substance, not the absence of the pancreas
itself, that causes diabetes. A method was devised for obtaining an
extract from these islands of Langerhans, and it was found that when
this extract was injected into a dog whose pancreas has been removed
it did not die, but got well and continued to be well as long as it
was given injections of this extract. After these injections had been
proved to be safe by repeated experiments on dogs, they were tried
on human patients with startlingly beneficial results. Even when the
disease is of long standing, when the patient has reached the very last
stage and is in the coma that immediately precedes death, injections of
this extract, now known to the world as insulin, will bring him out of
the coma, snatch him from the very jaws of death, and restore him to
health.
[Illustration:
_Pacific and Atlantic_
_Not man alone, but animals also have benefited by experimental work.
The best example of this is the conquest of hydrophobia._]