A HISTORY OF SCIENCE 



thither; from the centre to the extremities, to wit, 

 and from the extreme parts back again to the centre. 

 Finally, upon grounds of circulation, with the same 

 elements as before, it will be obvious that the quantity 

 can neither be accounted for by the ingesta, nor yet be 

 held necessary to nutrition. 



" Now let any one make an experiment on the arm 

 of a man, either using such a fillet as is employed in 

 blood-letting or grasping the limb tightly with his 

 hand, the best subject for it being one who is lean, 

 and who has large veins, and the best time after 

 exercise, when the body is warm, the pulse is full, and 

 the blood carried in large quantities to the extremities, 

 for all then is more conspicuous; under such circum- 

 stances let a ligature be thrown about the extremity 

 and drawn as tightly as can be borne : it will first be 

 perceived that beyond the ligature neither in the 

 wrist nor anywhere else do the arteries pulsate, that 

 at the same time immediately above the ligature the 

 artery begins to rise higher at each diastole, to throb 

 more violently, and to swell in its vicinity with a 

 kind of tide, as if it strove to break through and over- 

 come the obstacle to its current; the artery here, in 

 short, appears as if it were permanently full. The 

 hand under such circumstances retains its natural color 

 and appearances; in the course of time it begins to 

 fall somewhat in temperature, indeed, but nothing is 

 drawn into it. 



" After the bandage has been kept on some short 

 time in this way, let it be slackened a little, brought to 

 the state or term of middling tightness which is used in 

 bleeding, and it will be seen that the whole hand and 



