In June 1773 he was elected to the Chair of the Institutes of Medicine. This chair had been practically vacant for three years, during which time it was offered over and over again to Alexander Monro Drummond, whose chief merit seems to have been that he united the names of the great teaching Monroes with that of Drummond, perhaps the noblest citizen Edinburgh has ever had. It has been suggested, however, that this was only done to keep the appointment open for Gregory, when he should have completed his studies, and certainly when he returned, his election was unanimous. He entered upon his duties with happy vigour. Teaching was, as with every Gregory, his greatest gift, and the classes grew steadily all the time he was professor. The university never made greater progress than it did about this time, the medical graduates rising in number from about twenty in 1776 to one hundred and sixty in 1827. In the teaching of his class Professor Gregory daily felt the need for his students of a new book on the Theory of Medicine, so he wrote the _Conspectus Medicinae Theoreticae_ which proved such a valuable handbook on the subject. This book was most successful, it passed through many editions, was translated into English and several other languages, was used sometimes as a medical book and sometimes as a Latin text, for the Latin was as much admired as the information which it imparted. Considering the success of this volume, it is surprising that this was James Gregory’s only medical publication: he alas wrote many books afterwards, but with the exception of some chapters on philology and some literary essays, he wrote nothing but controversial works, prodigiously long, violent, personal, and acrid; their only excuse that they were never written for selfish ends and their only merit that they were a source of infinite amusement to the general public. Gregory lived in his father’s old house, No. 15 Canongate, and to this home he brought his first wife, the gentle Galloway girl, called Mary Ross, whose companionship was his, for such a short time in life’s journey. She died in 1784. In the years following her death he resumed his early classical studies, and it is a rather curious fact that he wrote nearly all the Latin epitaphs or dedications which were wanted for any purpose in Edinburgh from this time till his death. Principal Shairp, referring to Burns’ meeting with Gregory at Ochtertyre, describes how the poet ‘was charmed with the conversation of that last of the Scottish line of Latinists, which began with Buchanan and ended with Gregory.’