The bell was so thin and sensitive to the slightest jar or movement that, although it had been handled with extreme care, the captives could see that it was vibrating considerably, and the room was filled with a low metallic sound that not only affected the ear of the hearer but set every nerve to tingling. The medical man stopped the sound by laying his hand upon the bell. To a tube in the top of the bell he fastened one end of a rubber pipe; the other end was finished with a silver device shaped like the mouth-piece of a speaking tube. This he firmly pressed over the Englishman's heart. Thorndyke winced and bit his lip, for the strange thing took hold of his flesh with the tenacity of a powerful suction-pump.
“Ouch!” he exclaimed playfully, but Johnston saw that he had turned pale, and that his face was drawn as if from pain.
“Hold still!” ordered the medical man; “it will be over in a minute; now, be perfectly quiet and listen to the bell!”
The Englishman stood motionless, the sinews of his neck drawn and knotted, his eyes starting from their sockets. Thorndyke felt the rubber tube quiver suddenly and writhe with the slow energy of a dying snake, and then from the quivering bell came a low, gurgling sound like a stream of water being forced backward and forward.
Tradmos and the medical man stepped to the bell and inspected a small dial on its top.
“What was that?” gasped the Englishman, purple in the face.
“The sound of your blood,” answered Tradmos, as he removed the instrument from Thorndyke's flesh; “it is as regular as mine; you are very lucky; you are slightly fatigued, but you will be sound in a day or two.”
“Thank you,” replied the Englishman, but he sank into a chair, overcome with weakness.
“Now, I'll take you, please,” said the medical man, motioning Johnston to rise.
“I am slightly nervous,” apologized the latter, as he stood up and awkwardly fumbled the buttons of his coat.