730 GENERAL THERAPEUTIC MEASURES 



in fact, a species of local blood-letting by directly draining 

 blood away from the brain ; and it preserves life by pre- 

 venting pressure on, and paralysis of, the great vital medul- 

 lary 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 mem- 

 branes. 



In cerebral congestion, and dyspnoea due to gastric 

 tympany and pressure on the diaphragm, bleeding may give 

 relief. Blood-letting is particularly applicable in the treat- 

 ment 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. 

 Venesection alleviates dangerous pulmonary congestion, 

 removes the venous load on the right heart, and relieves 

 dyspnoea and cyanosis by making it possible for the heart to 

 force a smaller quantity of blood through the less obstructed 

 lungs. 



A feeble and easily compressible pulse does not neces- 

 sarily contraindicate 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 anaemia. Therefore, so 

 far from coutraindicating blood-letting, this condition urg- 

 ently demands it. Alarming dyspnoea, great cyanosis, 

 together with a general plethoric state, should guide us in 

 blood-letting in sthenic pneumonia and pulmonary conges- 

 tion, 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 dyspnoea' — by relieving the obstruction to the right 

 heart. Moderate blood-letting is occasionally useful in 

 severe cases of acute pleuritis, laminitis, lymphangitis and 

 urticaria in plethoric horses. 



Finally, in various toxaemias, blood-letting drains away 

 both the blood and its contained poison. The mass of 

 blood removed may be advantageously replaced by injection 



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