86 Veterinary Medicine. 



pave the way for their rupture and for blood effusion. Emboli 

 also carried from the diseased heart not onl}- cut off the blood 

 from the parts supplied b}' the plugged arteries, but increase the 

 blood tension on the cardiac side of the obstruction and endanger 

 rupture at any weak part. Thus they may cause apoplexy from 

 anaemia without rupture or apoplexy from the pressure of effused 

 blood. 



Age which is such a notorious factor in man is not without its 

 influence in the lower animals. It is in the old that we mostly 

 see disease of kidneys and heart and the degenerations of the tis- 

 sues, including the brain and its vessels ; in these, therefore, rupt- 

 ure and extravasation are the most frequent. 



The other causes are mostly connected with increased blood 

 tension with or without a debility of the vascular walls. Violent 

 exertions as in racing, coursing, dragging heavy loads up hill or 

 on heav}' ground, severe excitement, cerebral concussion, insola- 

 tion, and intense congestion of the brain substance have all been 

 recognized as causative factors. The compression of the jugulars 

 by a small collar, the violent straining attendant on parturition, 

 or constipation, and even the retrocession of blood from the sur- 

 face when exposed to extreme cold, may contribute to the final 

 rupture. 



In infectious diseases in which the toxic products tend to pro- 

 duce profound modifications in the blood and tissues, extravasa- 

 tions are met with in the brain as in other organs. Thus they are 

 seen in anthrax, Texas fever, petechial fever, etc. \ 



Then the formation of neoplasms in the l)rain may be the oc- 

 casion of the rupture of the vascular walls and apoplex3^ 

 Haematoma of the dura in the dog (Friedberger and Frohiier), 

 cholesteatomata in the horse, and carcinoma may be apparent 

 causes. 



The effect of mechanical injury must be admitted, as blows 

 on the head, injuries from an ox yoke, and concussions during 

 the battles of rams and bulls. 



Lesions. Blood extravasations may be found at anj' part of the 

 brain : a. into the the brain substance ; b. into the ventricles ; 

 c. from the pia mater ; d. into the arachnoid sac ; e. between 

 the skull and dura mater. It is especially common in connection 

 with the ganglia adjoining the ventricles; the corpus .striatum. 



