THE BRAIN 183 



It is very often impossible to outline individual cells in 

 these compact lesions, and we are convinced that there is a 

 syncytial formation. (Plates XXI, XXII, and XXV, figs. 52, 

 54, and 60.) Fibrils cannot be demonstrated in relationship 

 to these cells except in late lesions at the periphery where 

 their presence leaves open the question of their origin; i.e., 

 whether from the surrounding neuroglia or from the cells of 

 the nodule. 



The number of polymorphonuclear leucocytes may be great, 

 exceeding that of other cells. Migration of polymorphonuclear 

 leucocytes can be seen from capillaries remote from the lesions. 

 Occasionally the number of polymorphonuclear leucocytes 

 suggests in appearance a pyogenic infection; but this reaction 

 we believe to be called forth by the necrosis resulting from 

 complete thrombosis of several adjacent capillaries. 



Lymphoid and plasma cells are absent in the vast majority 

 of lesions. Rarely a cell corresponding to a lymphoid cell is 

 encountered in a lesion. We have not seen typical plasma cells 

 in lesions, although Giemsa's stain is well adapted for their 

 identification, as can be demonstrated in the perivasculai 

 zones of infiltration in the majority of the brains studied. 

 Plasma cells at the periphery of the lesions are encountered, 

 but in relationship to capillaries. 



Rod cells arranged radially in the tissue surrounding these 

 lesions are quite common and we believe enter into the forma- 

 tion of the lesion. The lesions do not increase in size beyond 

 the dimensions given by Spielmeyer, i.e., 0.1 to 0.12 milli- 

 meters. The various stages of their formation may be seen in 

 the same brain and until the febrile period in typhus has 

 passed. 



We have not been able to study these lesions in human brains 

 later than twenty-four days after the onset of typhus; and in 

 guinea-pigs have not yet studied the brains of late recovered 

 cases. Nicol has found the lesions to persist as late as the 

 eighth week, and has found recognizable traces, i.e., cicatrices 

 three to four months after the onset of typhus. He describes 

 the healing of most of the lesions as taking place, without 



