210 DISEASES OF THE BRAIN 



almost exclusively cause embolism of the cerebral arteries, that is, ol 

 valvular disease of the heart, of endocarditis, or of severe destructive 

 disease of the lungs. The occurrence of these premonitory symptoms, 

 and the presence or absence of valvular disease, endocarditis, or severe 

 disease of the lung, have such an effect on the diagnosis betweem em- 

 bolism of a cerebral artery and other brain-diseases, that with the 

 same set of symptoms we may diagnose embolism if we find them, and 

 exclude it with certainty if they are absent. The sudden shutting off 

 of arterial blood from the part of the brain supplied by the obstructed 

 artery, instantly arrests its functional power. Experience shows that 

 emboli almost always lodge in the arteria fossae Sylvii, particularly 

 the left one ; as the closure of this large artery causes great anaemia 

 of the parts supplied by it, we may readily see that sudden hemiple- 

 gia, especially of the right side, is the most important symptom from 

 which we can diagnose embolus in the cerebral arteries, if it occur in 

 a patient with valvular disease, etc. The entire loss of consciousness, 

 the apoplectic attack, which usually accompanies the commencement 

 of Jiemiplegia, when the arteria fossae Sylvii is stopped by an embolus, 

 is more difficult to explain. I think that this symptom is most prob- 

 ably due to the diseased hemisphere being decidedly swollen by col- 

 lateral oedema, and that, as occurs in large extravasations of blood, the 

 opposite hemisphere is not sufficiently protected from the pressure by 

 the falx, which only offers a limited amount of resistance. In embo- 

 lism of peripheral arteries at least, I have always found a very decided 

 and wide-spread cedema in the vicinity of the obstructed vessel, and 

 have witnessed considerable enlargement of the spleen from embolism 

 of the splenic artery. It is evident that a hemiplegia occurring sud- 

 ienly with an apoplectic attack may readily be mistaken for a cerebral 

 haemorrhage. In some cases, it is true, the age of the patient gives 

 grounds for distinguishing a hasmorrhage from an embolism. Haemor- 

 rhages occur chiefly, although not exclusively, in advanced age, embo- 

 lism comes in persons of any age ; hence, in young persons, the pre- 

 sumption is in favor of embolism. However, the only way of avoiding 

 error is the careful examination of the heart and lungs. The certainty 

 that the diagnosis receives from the discovery of valvular disease is 

 still more increased if we can also find a coincident embolism of a pe- 

 ripheral artery or of one of the internal organs, such as the spleen or 

 kidney. In most cases death occurs sooner or later after the attack, 

 with the symptoms of general paralysis ; in other cases consciousness 

 returns after a time. The symptoms of paralysis rarely disappear ; this 

 is sufficiently explained, as we have previously shown, by the difficult 

 establishment of a collateral circulation. 



Partial anaemia of tne brain, due to collateral oedema in the vicinity 



