PARTIAL AN^EMU OF THE BRAIN. 201 



cents to leave their beds too early. To prevent the second danger from 

 temporary lessening of the heart's action in anaemic patients, besides 

 the horizontal position, we may order irritating remedies both by in- 

 halation and internally. The patients should not use these remedies 

 constantly, but only occasionally when they feel an attack threatening. 

 Indeed, it may be important to have Cologne-water or Hoffman's ano- 

 dyne instantly at hand on such an occasion. Trephining is occasion- 

 ally the only remedy for anaemia caused by encroachment on the cra- 

 nial cavity ; however, in recent times this is very properly limited to 

 those contractions of the space caused by depression of the cranial 

 bones. Paradoxical as it may seem on superficial observation, we must, 

 nevertheless, say that a venesection often has the best effect on the 

 course of anaemia of the brain due to a contraction of the intracranial 

 cavity. We shall give the reasons for this assertion more fully when 

 speaking of apoplexy, and shall only say here, that a venesection 

 hastens the escape of venous blood from the brain, and thus facilitates 

 the entrance of arterial blood. 



CHAPTER IV. 



AND EMBOLISM OF THE CEREBRAL ARTERIES SOFTENING. 



ETIOLOGY. Partial anaemia of the brain occurs 1. When the 

 access of blood to certain sections of that organ is prevented by closure 

 of the afferent vessels. 2. When collateral oedema develops in the 

 vicinity of apoplexies, of points of inflammation, and softening, and of 

 tumors, etc. 3. When the capillaries of certain sections of the brain 

 are compressed by extravasation of blood, by tumors, or other diseases 

 contracting the cranial cavity. 



In regard to the pathogeny of the first form of partial anaemia of 

 the brain, which develops in the parts supplied by obstructed arteries, 

 we must call attention to the following points : 



In rabbits, the symptoms of anaemia of the brain do not occur till 

 both carotids and both vertebral arteries have been ligated. If all 

 these vessels be not ligated, those that have been left free supply 

 plenty of blood, and the free anastomosis of the cerebral arteries 

 among themselves prevents anaemia even of those parts which draw 

 their blood chiefly from the vessels ligated. In the human being it is 

 somewhat different ; here, after ligation of one carotid, there is occasion- 

 ally a symptom which certainly depends on anaemia of one side of the 

 brain, that is, paralysis of the half of the body on the opposite side. 

 In other cases of ligation of the carotid in man, this symptom does no! 



