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blood. The experiments to which I refer are put upon record in a letter of Harvey's to P. M. Slegel, of date 1651 (see Harveii Opera, ed. 1766, p. 613; ed. Willis, p. 597). They were undertaken with the object of giving a final and happy despatch to all the quibbling objections of Riolanus, ' omnes Riolani circa hanc rem altercationes jugu- lare;' and they consisted, firstly, in forcing water from the cava into the right ventricle whilst the pulmonary artery, the 'vena arteriosa' of those days was ligatured — whereby Riolanus' suggestion as to the permeability or porosity of the interventri- cular septum was shown to be untenable ; and, secondly, in forcing water from the pulmonary artery round into the opened left ventricle, whereby the lesser circulation was demonstrated, to use Harvey's own favourite word, avTo^ta ; or, to use the very words employed by him upon this very oc- would probably have accepted this alternative. It is right to add, however, that so far as ray reading of the edition of 1766 has carried me, I have come upon no other case where I have been forced to think that Dr. Lawrence may have blundered.