"Who, Sergeant, who? Who could have taken that bite? Mr. Schurman did not do it. His teeth did not fit; I looked. The teeth of the housekeeper and the maid did not do it; I looked at their teeth. All of the housekeeper's upper teeth are artificial, she wears a plate. The maid has all her own teeth. "This model shows that the person who bit into the apple, has a two tooth bridge on the upper jaw. The left lateral incisor is attached to the left canine, the eye tooth." "But my God, Professor, you are setting up teeth marks against fingerprints. Teeth marks, well what's the difference between teeth marks. Some may be different, but--" "Tooth marks, Sergeant, are as distinctive as fingerprints. No two single objects in the whole wide world are alike. No two red blood corpuscles coming from the same blood stream are precisely alike. True, they may differ only microscopically, but they differ nevertheless." "Professor," asked Jimmy, "couldn't two artificial sets of teeth be alike?" "Of course not! While the teeth are moulded by machinery, they are set up on a model of the individual's mouth by hand. And can you conceive a human pair of hands setting up two sets of teeth precisely alike? It is unthinkable." "But, Professor," pursued Conners, "lookit the case we got against this bird. There's his record. He always works his jobs this way; he left what we call his 'callin' card.' The large meal, the eggs the housekeeper says was missin' and last of all there's the nail file with his fingerprints. "You heard his alibi, Professor. He spent part of the night with friends of his, other crooks. He can't account at all for the hour or two before and after Schurman was killed." "The plaster models will be here, shortly, Sergeant. You can then see for yourself. All you say is correct but you must, before you convict him, account for the tooth marks in that apple. That is of the utmost importance, Sergeant." The plaster models of the upper and lower teeth of the prisoner came up in a short time. Professor Brierly held out the models and the moulage to the police officer: "Here, Sergeant, see if you can make them fit. You don't have to be a dentist to see that the teeth that bit into the apple are not the teeth of which these are models." Chapter XV As Professor Brierly, followed by the two younger men stepped into the busy city room, Hite held up a sheaf of telegrams that had come for the old scientist during his short absence. Professor Brierly took them as Hite said, "When you get through with these, Professor, I'll give you a message, a verbal message that I've got for you." Professor Brierly quickly ran through the messages. He looked up: