VENESECTION 515 



(24 to 48 hours) through absorption from the tissues and alimentary 

 canal. The heart beats more rapidly, owing to the lessened resistance 

 in the vessels, and venesection is accompanied by nausea and prostration. 



The blood is less dense and more fluid after blood-letting, and for 

 this reason, if inflammatory processes follow, exudation is more apt to 

 ensue. The fibrin is first regained, then the normal number of white, and 

 finally that of red corpuscles, in from one to five weeks. Circulatory 

 depressants — as veratrum viride — accomplish much the same results as 

 blood-letting, by causing general reduction of vascular tension and relief 

 from local congestion, thus "bleeding an animal into its own veins" with- 

 out loss of blood, it is true, but with less rapid and certain effect. 



Cathartics, diuretics and diaphoretics also lower blood pressure by 

 abstraction of fluid from the vessels, but their action is slow. The fol- 

 lowing disorders are those most suitable for treatment by venesection 

 when they exist in an alarming form in robust animals: 



Cerebral congestion. In isolation and Stlienic pneumonia. 



tympanites. Stlienic pleuritis. 



Apoplexy, particularly parturient apo- Urticaria. 



plexy of cows. Lymphangitis. 



Acute cerebral meningitis. Azoturia. 



Active pulmonary congestion and apo- Toxemia, bacterial. 



plexy. ■ Toxemia, mineral. 



Passive pulmonary congestion in car- Toxemia, vegetable. 



diac disease. (Followed by saline infusion.) 



Venesection from the jugular in cerebral congestion is, in fact, a 

 species of local blood-letting by directly draining blood away from the 

 brain; and it preserves life by preventing pressure on, and paralysijS of, 

 the great vital medullary centres controlling the respiration and heart. 

 Moderate blood-letting is sometimes advisable in the early stages of 

 severe inflammatory attacks of the brain or its membranes. 



In cerebral congestion, and dyspnea due to gastric tympany and 

 pressure on the diaphragm, bleeding may give relief. Blood-letting was 

 formerly used in the treatment of parturient apoplexy of cows, and, when 

 the disease has once occurred, it may be employed as a prophylactic 

 measure in plethoric animals immediately before parturition. Venesec- 

 tion alleviates dangerous pulmonary congestion, removes the venous load 

 on the right heart, and relieves dyspnea and cyanosis by making it pos- 

 sible for the heart to force a smaller quantity of blood through the less 

 obstructed lungs. 



A feeble and easily compressible pulse does not necessarily contra- 

 indicate venesection in engorgement of the lungs, for this condition leads 

 to stasis in the pulmonary circulation, prevents the proper flow of blood 

 into the left ventricle, and thus causes arterial anemia. Therefore, so 

 far from contraindicating blood-letting, this condition urgently demands 

 it. Alarming dyspnea, great cyanosis, together with a general plethoric 

 state, should guide us in blood-letting in sthenic pneumonia and pulmonary 

 congestion, rather than the state of the pulse. Venesection is serviceable 

 in advanced cases of cardiac disease in dogs — with failing compensation, 

 venous engorgement of the lungs, and dyspnea — by relieving the obstruc- 



Digitized by Microsoft® 



