terms which they said had no more to do with physic on the human body than a carpenter has in making Venice treacle or curing a fever Once accepted, men had a feeling that so important a discovery must change all the usual conceptions of disease. As has been said before, Harvey tells that he had in preparation a Practice of Medicine conformable to his Thesis of the Circulation of the Blood, and it soon became customary to put in the title-pages of works some reference to the new doctrine. Even Riolan’s Opuscula Anatomia makes an allusion to it. Walaeus, a keen defender of Harvey, published in 1660 a little compendium of practice ad circulationem sanguinis adornata, but there is nothing in it to suggest any radical change in treatment. Rolfinck’s Dissertationes Anatomicae, 1650, embracing the older and more recent views in medicine are ad circulationem accommodatae, and even as late as 1690 the well-known anatomy of Dionis was suivant la circulation. With the loss of his work on the Practice of Medicine it is impossible to say whether Harvey’s own practice was modified in any way. To part from the spirits and humours must have left his attitude of mind very sceptical, and that his ‘therapeutic way’ was not admired (as Aubrey tells us) speaks for a change which may have set many against him. More important than any influence upon treatment was, the irresistible change in the conceptions of disease caused by destruction of the doctrine of spirits and humours, which had prevailed from the days of Hippocrates. While Harvey, as he says, had in places to use the language of physiology, that is, the language of the day, he makes it very clear, particularly in the second letter to Riolan, that he will have none of the old doctrine to which the de Motu Cordis dealt the death blow.