60 CIRCULATION OF THE BLOOD 



1 Further, when the bandage is relaxed from extreme 

 tightness [to moderate tightness], we see the veins below 

 the bandage instantly swell up and become gorged, while 

 the arteries meantime continue unaffected, this is an ob- 

 vious indication that the blood passes from the arteries 

 into the veins, and not from the veins into the arteries." 



This shows that there must therefore be either an 

 anastomosis of the two [kinds] of vessels, or passages in 

 the flesh and solid parts that are permeable by the blood. 

 It shows too that the veins themselves have frequent 

 communications with one another, because they all be- 

 come turgid together, with the moderately tight bandage 

 . . . and, moreover, if any single small vein be then 

 pricked with a lancet, they all speedily shrink." 



15. " We have now spoken of the blood that passes 

 through the heart and the lungs . . . [and of the blood 

 that passes] from the arteries into the veins in the peri- 

 pheral 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 external to the central parts." 



The celebrated Hieronymus Fabricius of Aquapen- 

 dente, a most skilful Anatomist, and venerable old man 

 . . . made representations of valves in the veins. . . . 

 These are situated at different distances from each other, 

 and diversely in different individuals . . . and are directed 

 upwards or towards the trunks of the veins. . . . (Plate 

 VII. Fig. 5.) If therefore anything attempted to pass from 

 the trunks into the branches of the veins, or from the greater 

 vessels into the less, they completely prevent it. ..." 



The discoverer of these valves did not rightly under- 

 stand their use, nor have others added anything to our 

 knowledge. Their function is by no means explained 

 when we are told that it is to hinder the blood, by its 



