62 MOTION OF THE 



action of the heart, and its diminished impelling power, the 

 stream cannot make its way under the fillet ; and farther, owing 

 to the weak and languishing state of the heart, the blood 

 is not transferred in such quantity as wont from the veins to 

 the arteries through the sinuses of that organ. So also, and 

 for the same reasons, are the menstrual fluxes of women, and 

 indeed hemorrhagies of every kind, controlled. And now, a 

 contrary state of things occurring, the patient getting rid of his 

 fear and recovering his courage, the pulsific power is increased, 

 the arteries begin again to beat with greater force, and to drive 

 the blood even into the part that is bound ; so that the blood 

 now springs from the puncture in the vein, and flows in a con- 

 tinuous stream. 



CHAPTER XIII. 



THE THIRD POSITION IS CONFIRMED : AND THE CIRCULATION OP 

 THE BLOOD IS DEMONSTRATED PROM IT. 



THUS far have we spoken of the quantity of blood passing 

 through the heart and the lungs in the centre of the body, and 

 in like manner from the arteries into the veins in the peripheral 

 parts and the body at large. We have yet to explain, however, 

 in what manner the blood finds its way back to the heart from 

 the extremities by the veins, and how and in what way these 

 are the only vessels that convey the blood from the ex- 

 ternal to the central parts ; which done, I conceive that the 

 three fundamental propositions laid down for the circulation of 

 the blood will be so plain, so well established, so obviously true, 

 that they may claim general credence. Now the remaining 

 position will be made sufficiently clear from the valves which 

 are found in the cavities of the veins themselves, from the uses 

 of these, and from experiments cognizable by the senses. 



The celebrated Hieronymus Fabricius of Aquapendente, a 

 most skilful anatomist, and venerable old man, or, as the 

 learned Riolan will have it, Jacobus Silvius, first gave represen- 

 tations of the valves in the veins, which consist of raised or loose 

 portions of the inner membranes of these vessels, of extreme 

 delicacy, and a sigmoid or semilunar shape. They are situ- 



