Whyland obeyed, and after some fumbling contrived to reach the exact spot. “Yes, it can be done, but it’s precious awkward,” he remarked, handing the syringe back.

“Exactly,” agreed the doctor. “That may account for the needle having broken off. Mind, I’m only suggesting a possibility, not laying down a theory. That’s your job. Now we come to the white incrustation round the puncture. Unless I’m greatly mistaken, it is potassium carbonate. Should it prove to be so, the fact would be of considerable significance.”

“Why?” enquired Whyland. “I’m afraid I don’t quite follow you, doctor.”