820 THE NERVOUS SYSTEM. 



Marie notes in addition, atrophy and disappearance of the cells of Clarke's column. 

 Blocq and Marinesco 1 describe degeneration of the posterior root fibres similar to that 

 found in tabes. Friedreich 2 and Riitimeyer 3 find atrophy of the anterior horn cells. 

 The determining cause of the disease and the nature of the morbid process are as yet 

 undetermined. It seems probable that the condition of the cord may be more properly 

 considered an abnormality of development rather than a degeneration. 



CEREBELLAR ATAXIA. 



Atrophy of the cerebellum was noted as sometimes occurring in Fried- 

 reich 's ataxia. In that disease, however, the cord lesion was most 

 marked. In cerebellar ataxia the lesion of the cord is slight or absent, 

 the chief lesion being an atrophy of the cerebellum. This atrophy is 

 accompanied by little or no sclerosis, the organ being simply smaller 

 than normal. 



INFLAMMATION. 



INFLAMMATION OF THE BRAIN. (Encephalitis.} 



Acute Encephalitis, Inflammatory processes in the nervous system, 

 whether of an exudative or of a productive type, are frequently consecu- 

 tive to or coincident with the more severe forms of degeneration or other 

 lesions, thus making differentiation of the processes often extremely dif- 

 ficult. It has been already mentioned that the brain tissue about haemor- 

 rhages and areas of embolic and thrombotic softening may undergo in- 

 flammatory changes leading to the formation of new connective tissue. 

 There is a class of cases in which localized areas of the brain undergo 

 softening, with more or less extravasation of red and white blood cells 

 and hypersemia, so that the softened material consists, as seen under the 

 microscope, of detritus of brain tissue in a condition of fatty degenera- 

 tion, often with more or less pus cells and pigment. When such areas are 

 red in color from intermingled blood cells or pigment, the condition is 

 called red inflammatory softening. When fatty degeneration prevails, and 

 the red blood cells or their derivatives are not abundant, the softened 

 area looks yellow or yellowish-white, and this is often called yellow in- 

 flammatory softening. The origin of these processes is very obscure and 

 their inflammatory nature not well defined. 



ABSCESS OF THE BRAIN. Small multiple abscesses of the brain may 

 occur in pyaemia. Large abscesses of the brain are usually single ; they 

 may attain a large size. They are most frequent in the cerebral and 

 cerebellar hemispheres, rare in the basal ganglia, the pons, and the 

 medulla oblongata. 



There may be an irregular cavity containing thin pus and softened 



1 Blocq, P. and Marinesco, O., "Sur 1' Anatomic Pathologique'de la Maladie de Fried 

 reich." Compte rend. Soc. de Biol., 1890. 



2 Friedreich, N., Virchow's Arcliiv, Bd. 86, 1881. 



3 Riitimeyer, L., Virchow's Arcliiv, Bd. 110, 1887. 



