MOTION OF THE HEART AND BLOOD 



may cause gangrene in the limbs, and what their 

 function may be in castrating animals or removing 

 fleshy tumors. 



Because no one has understood the rationale 

 of these matters, it has happened that almost every- 

 one recommends ligatures in treating disease on the 

 authority of the ancients, and very few use them 

 properly or get any benefit from them. 



Some ligatures are tight, others middling. I 

 call a ligature tight when it is pulled so firmly about 

 a limb that the beat of the artery cannot be felt 

 beyond it. We use this kind in amputations to 

 control bleeding. This kind is also used in castrating 

 animals and removing tumors, where we see the tes- 

 ticles and tumors dying and dropping off because 

 the ligature keeps out heat and nourishment. 



I call a ligature middling which compresses a 

 limb on all sides, but without pain, so that the 

 artery may still pulsate somewhat beyond the 

 ligature. This type is used for "drawing," in blood- 

 letting. The proper ligature for phlebotomy is applied 

 above the elbow in such a manner that the artery at 

 the wrist may still be felt beating slightly. 

 ,^ Now, let an experiment be made on a man's 

 arm, using a bandage as in blood-letting, or grasp- 

 ing tightly with the hand.^ The best subject is one 



' These interesting experiments, discussed in a quantitative way 

 in Chapter XIII, imply some of the factors involved in arterial and 

 venous blood pressure. Attention was sharply drawn to the mechanical 

 relations of blood-pressure by the Rev. Stephen Hales (1677-1761) and 



[85] 



