Edward bowed, and left us.  While I had been seeking him, Kennedy had telephoned hastily to his laboratory and had found one of his students there.  He had ordered him to bring down an apparatus which he described, and some other material.

While we waited Kennedy sent word to Pitts that he wanted to see him alone for a few minutes.

The instrument appeared to be a rubber bulb and cuff with a rubber bag attached to the inside.  From it ran a tube which ended in another graduated glass tube with a thin line of mercury in it like a thermometer.

Craig adjusted the thing over the brachial artery of Pitts, just above the elbow.

“It may be a little uncomfortable, Mr. Pitts,” he apologised, “but it will be for only a few minutes.”

Pressure through the rubber bulb shut off the artery so that Kennedy could no longer feel the pulse at the wrist.  As he worked, I began to see what he was after.  The reading on the graded scale of the height of the column of mercury indicated, I knew, blood pressure.  This time, as he worked, I noted also the flabby skin of Pitts as well as the small and sluggish pupils of his eyes.

He completed his test in silence and excused himself, although as we went back to the kitchen I was burning with curiosity.

“What was it?” I asked.  “What did you discover?”

“That,” he replied, “was a sphygmomanometer, something like the sphygmograph which we used once in another case.  Normal blood pressure is 125 millimetres.  Mr. Pitts shows a high pressure, very high.  The large life insurance companies are now using this instrument.  They would tell you that a high pressure like that indicates apoplexy.  Mr. Pitts, young as he really is, is actually old.  For, you know, the saying is that a man is as old as his arteries.  Pitts has hardening of the arteries, arteriosclerosis—­ perhaps other heart and kidney troubles, in short pre-senility.”

Craig paused:  then added sententiously as if to himself:  “You have heard the latest theories about old age, that it is due to microbic poisons secreted in the intestines and penetrating the intestinal walls?  Well, in premature senility the symptoms are the same as in senility, only mental acuteness is not so impaired.”

We had now reached the kitchen again.  The student had also brought down to Kennedy a number of sterilised microscope slides and test-tubes, and from here and there in the masses of blood spots Kennedy was taking and preserving samples.  He also took samples of the various foods, which he preserved in the sterilised tubes.

While he was at work Edward joined us cautiously.

“Has anything happened?” asked Craig.

“A message came by a boy for Mrs. Pitts,” whispered the valet.

“What did she do with it?”

“Tore it up.”

“And the pieces?”

“She must have hidden them somewhere.”

“See if you can get them.”