PARTIAL ANJEMIA OF THE BRAIN. 207 



other local diseases there, by basing our diagnosis on the etiological 

 conditions, the sequence of the symptoms, the existence of symptoms 

 corresponding to the peculiar frequence of certain forms of disease in 

 certain sections of the brain, as well as on the course of the disease. 



We shall first describe the symptoms of the occurrence and course 

 of partial anaemia of the brain due to obstruction of the vessels, and 

 show how it is often possible to diagnose this form of partial anaemia 

 with probability or with certainty by attending to the inducing causes. 

 However, the etiology of thrombosis of the cerebral vessels differs 

 from that of embolism, and the other factors also, which might be of 

 aid in diagnosis, are not exactly the same in thrombosis and embolism 

 of the cerebral arteries ; hence we shall speak of them separately. 



Since thrombosis of the cerebral vessels most frequently depends 

 ultimately on atheromatous degeneration of the vascular walls, and as 

 this occurs chiefly in old age, we are more apt to suspect thrombosis, 

 and consequent softening of the brain, in an old, decrepit person, who 

 has the symptoms of severe brain-trouble, than in a young, vigorous 

 one, having the same symptoms. If the peripheral arteries be rigid 

 and tortuous, there is still greater presumption that the arteries of the 

 brain are also degenerated, and that the brain-symptoms are due to 

 this degeneration. However, the condition of the peripheral arteries 

 does not furnish any certain proof of that of the cerebral arteries. In 

 many cases the degeneration is confined to the latter ; in other, rarer 

 cases, while the peripheral arteries are extensively degenerated, the 

 cerebral arteries remain free. Moreover, partial anaemia of the brain, 

 and softening of the brain due to necrosis of the anaemic portion, is 

 not the only brain-disease caused by atheromatous degeneration of the 

 cerebral arteries. Experience shows that atheromatous degeneration 

 of the walls of the vessels usually induces dilatation of the larger 

 arterial trunks, and, on the contrary, contraction of the smaller arteries. 

 The atheromatous arteries of the brain are also usually contracted for 

 a long while before they are closed by thromboses. Hence the symp- 

 toms of thrombosis, or, rather, of the partial anaemia and partial ne- 

 crosis of the brain depending on it, are almost always preceded by 

 premonitory symptoms, either of disturbance of circulation, induced 

 by the contraction of certain cerebral vessels, or by symptoms of 

 senile cerebral atrophy, which has been caused and hastened by de- 

 generation of the cerebral vessels. The patients complain of pain in 

 the head, dizziness, ringing of the ears, flashes before the eyes, loss of 

 memory and power of thought; they are apathetic and indifferent, 

 and much inclined to sleep, but their sleep is disturbed by uneasy 

 dreams. As a rule, very small arteries are at first obstructed, either 

 by the atheromatous process causing their entire obliteration, or be- 



