CHAPTEE X. 



OPERATIONS ON THE CIRCULATORY 



SYSTEM. 



BLEEDING— VENESECTION. 



The term bleeding, or venesection, signifies the opening of 

 certain veins for the escape of a portion of the blood, for a ther- 

 apeutical, or experimental purpose. If it is designed to reduce 

 the volume of the circulation, it is known as general, and is per- 

 formed upon some one of the larger blood vessels ; if practiced 

 to remove blood only from a given region, it becomes local, and 

 in that case the smaller vessels are divided. A better division is 

 that which is based on the nature of the vessel which is opened, 

 and thus it is phlebotomy, if a vein is opened; arteriotomy, if 

 an artery ; and capillary, or arterio-phlebotomy, when the opera- 

 tion is practiced upon the capillary system. 



There has been much discussion upon the question of the 

 utility of blood-letting, and strong advocates and earnest oppo- 

 nents, who have argued its benefits and denied its usefulness, and, 

 in fact, ascribed evil results to its practice, whether the depletion 

 afi^ects the general circulation or a limited region. But upon this 

 we shall not enter. Those who maintain its practice consider it 

 to be indicated when it is desirable to reduce the activity of the 

 circulation, or, on the contrary, to stimulate it in parts where, 

 from different causes, it has been temporarily suspended, and to 

 stimulate absorption, or to relieve the organism of foreign ele- 

 ments. 



It is, however, contra-indicated in all eruptive fevers, in anaemic 

 patients, and in those suffering with typhoid diseases. 



The old fashion of " taking blood" as a prophylactic measure, 

 or at a certain season of the year, is simply the result of an ignor- 

 ant delusion. 



The quantity of blood that can be removed must vary, of 

 course, with the size, the nature and the condition of the animal. 



