Abstract
The writer had tried a comparative test of bone conduction of sound through the teeth, the mastoid process, and the frontal with 100 persons of normal hearing, and proved it to be more effective through the teeth than the other two parts. He has now made a further test with a special apparatus in order to get more conclusive results. By means of photographs, he has compared the vibrations of bone conduction of a living person's head and a skull through the mastoid process, the frontal, and the teeth, and has proved that through the teeth to be the strongest for every direction, and that through the frontal to be the weakest.
