Dust out of pockets, or in the recesses of a pocket-knife, and so on, if closely examined, tells a great deal.
Then on another occasion a murder was committed, and close by a cap was found which did not belong to the victim, so probably it belonged to the murderer. Two hairs were found sticking to the lining of the cap; they were carefully taken to Dr. Emile Pfaff, a celebrated observer. He examined the hairs under a microscope and was able to read from them that the owner of the cap was "A man of middle age, strong, inclined to be fat; black hair with some grey among it, getting bald; lately had his hair cut."
In this way a clue was got to the appearance of the murderer.
Dr. Bell of Edinburgh is said to be the original from whom Sir Conan Doyle drew his idea of Sherlock Holmes.
The doctor was once teaching a class of medical students at a hospital how to doctor people. A patient was brought in, so that the doctor might show how an injured man should be treated. The patient in this case came limping in, and the doctor turned to one of the students and asked him:
"What is the matter with this man?"
The student replied, "I don't know, sir. I haven't asked him yet."
The doctor said, "Well, there is no need to ask him, you should see for yourself—he has injured his right knee; he is limping on that leg: he injured it by burning it in the fire; you see how his trouser is burnt away at the knee. This is Monday morning. Yesterday was fine; Saturday was wet and muddy. The man's trousers are muddy all over. He had a fall in the mud on Saturday night."
Then he turned to the man and said, "You drew your wages on Saturday and got drunk, and in trying to get your clothes dry by the fire when you got home you fell on the fire and burnt your knee—Isn't that so?"
"Yes, sir," replied the man.