Read it through once

“Very interesting reading it might be made, too,” remarked Sherlock Holmes, sticking a small piece of plaster over the prick on his finger. “I have to be careful,” he continued, turning to me with a smile, “for I dabble with poisons a good deal.” He held out his hand as he spoke, and I noticed that it was all mottled over with similar pieces of plaster, and discoloured with strong acids.