208 DISEASES OF THE BRAIN. 



cause their calibre is contracted, and then obstructed by a thrombosis. 

 The ansemia resulting from closure of these small vessels is limited in 

 extent, and hence may readily be removed by an increased supply of 

 blood through neighboring vessels. "We must bear this in mind when, 

 in a marasmic patient, who for some time has had the brain-symp- 

 toms that we designated as premonitory, limited regional symptoms 

 (herdsymptome) occur, and, after lasting for a time, disappear again. 

 Among these symptoms are inability to say different words, loss of 

 memory for certain names and numbers, pain, or a feeling of formica- 

 tion, or of certain limbs going to sleep, occasionally only of certain 

 fingers or toes, contractions and paralysis, which are also occasionally 

 limited to certain fingers or toes, etc. 



Many authorities have explained this variation of symptoms, par- 

 ticularly the occurrence and disappearance of paralysis, as a peculiar 

 symptom of softening of the brain. This is a false view of the matter. 

 In cases where the symptoms have presented this variation, if soften- 

 ing of the brain be found on autopsy, the softening did not occur at 

 the time the symptoms changed, but at a later period, when they were 

 constant. On the other hand, the occurrence and disappearance of 

 circumscribed paratyses are certainly, to some extent, characteristic of 

 partial anaemia of the brain resulting from atheromatous degeneration 

 and thrombosis of small cerebral arteries, and are rapidly removed again 

 by the establishment of collateral circulation. (The occurrence and 

 disappearance of circumscribed paralyses do not render it certain that 

 there is thrombosis of small arteries of the brain ; the same symptom 

 is also seen from small extravasations. See Chapter V.) If a large 

 artery, or several small ones going to the same part of the brain, be 

 closed by thrombosis, as we have already shown, a collateral circula- 

 tion cannot be established, particularly if the degeneration of the 

 walls of the vessels be extensive, and then the affected portion of 

 brain loses its functional power forever. There are some parts of the 

 brain for instance, the large medullary masses of the hemispheres 

 that may be destroyed without any apparent loss of function. This 

 fact, which is proved by numerous examples, explains the occurrence 

 of those cases of softening during whose course there have never been 

 any symptoms of paralysis. We must know this in order to under- 

 stand that it is occasionally quite impossible to diagnose softening 

 of the brain, and to distinguish it from simple senile atrophy, because 

 the most important point for the differential diagnosis is wanting. 

 But, far more frequently, the results of thrombosis of a large artery, 

 or of numerous small ones, extend to parts of the brain, whose loss of 

 function induces paralysis, and even hemiplegia, particularly to the 

 oorpus striatum and thalamus. The arteries supplying the great hemi- 



