232 DISEASES OF THE BRAIN 



In small animals the electric battery may be useful. In 

 chronic cases only a successful treatment of the basic disease 

 will heal the brain anemia. 



CONGESTION OF THE BRAIN AND ITS MEMBRANES. 



Brain congestion may be active, due to an engorgement of 

 the brain with arterial blood, or it may be passive, caused 

 by a stoppage of the outflow of venous blood. 



Etiology. — Passive congestion rarely produces symptoms 

 in animals. An active hyperemia of the brain can be caused 

 by an increased heart activity and the loss of tonus in the 

 cerebral arteries due to overwork, rough treatment of young 

 animals (breaking colts; the excitement of railway or ship 

 transportation); estrum; fright; hypertrophy of the heart; 

 acute alcohol poisoning; sunstroke and heatstroke. A collat- 

 eral congestion may result from compression of the large 

 bloodvessels of the abdomen in severe bloating of the stomach 

 or bowels. An active hyperemia of the brain is the first stage 

 of inflammation. 



A passive hyperemia occasionally occurs from compres- 

 sion of the jugulars, due to ill-fltting collars, too tight throat 

 latches ("choking down" of horses), tumors, inflammatory 

 swellings or enlarged thyroids which press upon the jugulars. 

 It may also be a symptom of heart weakness, chronic diseases 

 of the lung, or compression of the lung from gas accumulation 

 in the stomach or bowels. 



Symptoms. — ^The principal symptom of active hyperemia 

 is excitement, which usually is soon followed by a stage of 

 depression. The pupils are dilated, the mucous membrane 

 of the head congested, the pulse and respirations are 

 increased in frequency, and the poll feels warm. Very 

 probably, however, these symptoms represent a transient 

 inflammation of the brain often the result of a chronic 

 hydrocephalus, which occasionally "flares up" in this form. 



A severe passive hyperemia causes the animal to show 

 stupor, sopor, the mucous membranes cyanotic, the pulse 

 small and rapid, and the patient dyspneic. 



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