bellows to rayse water. Constat per ligaturam transitum sanguinis ab arterijs ad venas, unde A perpetuum sanguinis motum in circulo fieri pulsu cordis.
The two hyd atic conditions of the circula- tion are herein defined with geometrical accuracy, and read like the enunciation of a Theorem in Euclid. Indeed, it is remarkable what a strong mathematical element runs through the argument of both his great treatise and of the lectures; not of course mathematics as we now understand them, for at the date of Harvey's death, Newton was a boy of 15, but those of Euclid and of Archimedes. In the second page of the MS. work he speaks of form "ut trigonis in tetragonum," of proportion ut diapente in diapason," the relation of the triangle to the square, of the fifth in music to the octave. An even more remarkable reference to musical ratios occurs a few lines later, "ut semiditonos diapaso," like a semitone to an octave.
Again in the ninth page we find "Proportio pec- toris ad ventrem diapason ut 3.4 sesquitertia; pectoris ad caput diapente, pectoris ad alvum 2 diapason; both these last two ratios being expressed as fractions.
