The _medical_ opponents were, perhaps, the most powerful; certainly it was they who had first to be won over, for without the support of the profession the cause was in danger. It was urged first of all that the use of anaesthetics would increase the mortality, then very great, of surgical operations, and those who took their stand upon this ground were men who had at first denied the possibility of making operations painless, and had been driven to abandon that opinion only by a clear demonstration of the fact. To meet this form of opposition he instituted a laborious and extensive statistical investigation in order to compare the results obtained in hospitals where anaesthetics were used with those where the operations were performed on patients in the waking state. He took care that the reports dealt with the same operations under, as nearly as possible, similar conditions in each case. He obtained returns from close upon fifty hospitals in London, Edinburgh, Dublin, and various provincial towns. One of the most fatal operations in those days, and one dreaded by patient and surgeon alike, was amputation of the thigh. In 1845 Professor Syme said that the stern evidence of hospital statistics showed that the average frequency of death after that operation was not less than 60 to 70 per cent., or above one in every two operated upon. Simpson fearlessly collated statistics of this operation amongst the others, and proved that when performed under anaesthetics amputation of the thigh had its mortality reduced to 25 per cent. His figures were as follows:-- TABLE OF THE MORTALITY OF AMPUTATIONS OF THE THIGH. Reporter. Cases. Deaths. % of Deaths. Not anaesthetised. Parisian hospitals--Malgaigne 201 126 62 in 100 Edinburgh " --Peacock 43 21 49 " General collection--Phillips 987 435 44 " Glasgow hospitals --Lawrie 127 46 36 " British " --Simpson 284 107 38 " Cases on patients in an anaesthetised state 145 37 25 " He pointed to the above table as a proof that far from increasing the mortality of this operation the introduction of anaesthetics had already led to a saving of from eleven to twenty lives out of every hundred cases. He acknowledged that the number of cases he had collected (145) was somewhat small from a statistical point of view; but he confidently asserted that future figures would show greater triumphs. The tables of other operations showed similar results, and he entered exhaustively into the subject in a paper published in 1848. The paper was entitled, "Does Anaesthesia increase or decrease the mortality attendant upon surgical operations?" According to his wont, he headed it with a quotation from Shakspeare: "Why doest thou whet thy knife so earnestly? ... Shylock must be merciful. On what compulsion must I? Tell me that!"