"Some of them are," he replied. "Yesterday the chief of Police in a
Western city sent a man East to see me about the Price murder--you
know the case?"

Indeed I did. A wealthy banker of the town had been murdered on the
road to the golf club, no one knew why or by whom. Every clue had
proved fruitless, and the list of suspects was itself so long and so
impossible as to seem most discouraging.

"He sent me a piece of a torn handkerchief with a deep blood-stain
on it," pursued Kennedy. "He said it clearly didn't belong to the
murdered man, that it indicated that the murderer had himself been
wounded in the tussle, but as yet it had proved utterly valueless as a
clue. Would I see what I could make of it?

"After his man had told me the story I had a feeling that the murder
was committed by either a Sicilian laborer on the links or a negro
waiter at the club. Well, to make a short story shorter, I decided to
test the blood-stain. Probably you didn't know it, but the Carnegie
Institution has just published a minute, careful, and dry study of the
blood of human beings and of animals. In fact, they have been able to
reclassify the whole animal kingdom on this basis, and have made some
most surprising additions to our knowledge of evolution. Now I don't
propose to bore you with the details of the tests, but one of the
things they showed was that the blood of a certain branch of the
human race gives a reaction much like the blood of a certain group of
monkeys, the chimpanzees, while the blood of another branch gives a
reaction like that of the gorilla. Of course there's lots more to it,
but this is all that need concern us now.