296 LECTURE XII. 



a great part of the cell is filled up with it. The more 

 abundant it is, the darker does the whole spot appear to 

 the naked eye. 



Formerly it was imagined that the majority of ganglion- 

 cells were merely round bodies, but 

 the conviction has been gradually 

 gaining strength, that this form is an 

 artificial one, and that the real state 

 of the case is rather, that processes 

 strike out from the cell in various 

 directions, and ultimately become 

 continuous with nerves or other 

 ganglion- cells. These processes are 

 in the first instance pale, and even where their transition 

 into ordinary, darkly-contoured nerve-fibres can be 

 traced, they are observed (but generally not until a cer- 

 tain distance from the ganglion-cell) to become thicker 

 and gradually to provide themselves with a medullary 

 sheath. This circumstance which was formerly unknown 

 explains how it was, that during so long a period so 

 much obscurity prevailed with regard to these conditions. 

 In the first part of their course, therefore, the processes 

 of the glanglion-cells, especially in the brain and spinal 

 marrow, are not nerves in the ordinary meaning of the 

 word, but pale fibres which frequently bear scarcely any 

 resemblance to the non-medullated fibres I have already 

 described to you, and have rather the appearance of pale 

 axis-cylinders (Fig. 88, a, b). 



It was long believed that essential differences existed 

 between the ganglion-cells according as they belonged to 

 one or other of the three principal divisions of the 



Fig. 88. Elements from the Gasserian ganglion, a. Ganglion-cell with nucleated 

 sheath, which is prolonged around the efferent nerve-process; in the interior, the 

 large, clear nucleus with its nucleolus, and round about it an accumulation of pig- 

 ment, b. Isolated ganglion-cell with a pale process proceeding up to it. c. Deli- 

 cate nerve-fibre with pale axis cylinder. 300 diameters. 



