Belfield hastily slunk back into the office, locking the door after him, and Thorndyke, having returned the box to the laboratory and deposited the cards bearing the finger-prints in a drawer, came round to inspect my work. I had managed to detach a tiny fragment of dried clot from the blood-stained garment, and this, in a drop of normal saline solution, I now had under the microscope.
"What do you make out, Jervis?" my colleague asked.
"Oval corpuscles with distinct nuclei," I answered.
"Ah," said Thorndyke, "that will be good hearing for some poor devil. Have you measured them?"
"Yes. Long diameter 1/2100 of an inch; short diameter about 1/3400."
Thorndyke reached down an indexed note-book from a shelf of reference volumes and consulted a table of histological measurements.
"That would seem to be the blood of a pheasant, then, or it might, more probably, be that of a common fowl." He applied his eye to the microscope and, fitting in the eye-piece micrometer, verified my measurements. He was thus employed when a sharp tap was heard on the outer door, and rising to open it he admitted the superintendent.
"I see you are at work on my little problem,
