After Fauchard, the study of dentistry rapidly expanded. Two important books, "Natural History of Human Teeth" (1771) and "Practical Treatise on the Diseases of the Teeth" (1778), were published by British surgeon John Hunter. In 1763 he entered into a period of collaboration with the London-based dentist James Spence. He began to theorise about the possibility of tooth transplants from one person to another. He realised that the chances of a successful tooth transplant (initially, at least) would be improved if the donor tooth was as fresh as possible and was matched for size with the recipient. These principles are still used in the transplantation of internal organs. Hunter conducted a series of pioneering operations, in which he attempted a tooth transplant. Although the donated teeth never properly bonded with the recipients' gums, one of Hunter's patients stated that he had three which lasted for six years, a remarkable achievement for the period.