Meyer, Data of Modern Neurology. 253 



nerve-elements ; and acute degeneration in the cortex occurs in 

 different disease-processes with or without an adequate neuro- 

 gha-reaction. Nissl has spoken of this same discrepancy in his 

 discussion of the pathology of general paralysis. (Arch, f 

 Psych. Vol. 29). 



The literature on the nervous system contains signs of nu- 

 merous fluctuations in the views of the interrelations of these 

 constituents of the nervous tissues. We mention as a mere 

 curiosity the conception of Aristotle, for whom the blood- 

 vessels contained the active spirit, while the brain tissue was 

 merely a fat-lump to cool the excess of heat of the blood. In 

 our enlightened age, there is an improved edition of this view 

 to be found in a peculiar tendency of making the blood-supply 

 responsible for, and not merely a help of, the activity of the 

 ' nerve-cells. ' As hyperaemia was long held to be the cause of 

 inflammation, so Meynert has elaborated a remarkable system 

 of hyperaemias and anaemias for the explanation of rest and 

 activity of the nervous mechanisms and even for the explana- 

 tion of disease-complexes. Further we see to this day two 

 camps in the explanation of the pathological nature and starting 

 point of general paralysis. To a large number of investigators 

 the primary lesion seems the vascular alteration, while others 

 follow rather the views which Weigert has formulated, according 

 to which the parenchyma, the nerve-elements, are the sufferers 

 and draw with them the neuroglia and the blood-vessels, A 

 discussion of this burning problem would go far beyond my 

 present task ; it is mentioned here in order to urge with more 

 emphasis the absolute necessity of treating nerve-pathology 

 as the pathology of a tissue and not merely a pathology of 

 neurones. 



Another wave in the same line is the view which Cajal has 

 held for some time concerning the activity of neuroglia, Ca- 

 jal's brother Pedro has pronounced himself in favor of the view 

 that neuroglia serves to keep apart and isolate the nerve ele- 

 ments. Ramon y Cajal has observed that in an animal killed 

 while asleep the neuroglia processes were longer and therefore 

 ' isolated ' better than in an animal killed awake, and on this 



