210 



ON THE ELEMENTARY PARTS OF THE HUMAN FABRIC. 



[Fig. 114. 



a> 



115. 



Ganglion globules, with their processes, nuclei, and nucleoli: o. a. From the deeper part ol" the gray 

 mutter of the convolutions of the cerebellum. The larger processes are directed towards the surface 

 of the organ, b. Another from the cerebellum, c. d. Others from the post, horn of gray matter of the dor- 

 sal region of the cord. These contain pigment, which surrounds the nucleus in c. In all these specimens 

 the processes are more or less broken. Magnified 200 diameters.] 



Man and the higher animals at least, from the white substance composed of 

 nerve-tubes, of which the trunks of the nerves, as well as a large part of the 

 brain and spinal cord, are made up ; and occupying in the brain a position 

 external to the latter, which is often termed the medullary substance. This 

 position, however, is quite an exceptional one; for in the spinal cord and in 

 the scattered ganglia of Vertebrated animals, and in all the ganglionic centres 

 of (Invertebrata, everywhere, in fact, except in the Brain, the vesicular 

 nerve substance occupies the centres of the ganglia; consequently the terms 



cortical and medullary, as applied to the vesi- 

 cular and tubular substances respectively, are 

 quite inappropriate. Nor are the designations 

 that have reference to their colour, much more 

 uniformly correct: for, as we have seen, 

 the vesicular substance may be destitute of 

 internal pigment-granules, and the blood in 

 its capillary plexus may be pale or colourless, 

 so that the reddish-grey hue, which is ex- 

 pressed by the term cineritious, may be entirely 

 wanting; whilst, on the other hand, we have 

 seen that certain of the nerve-fibres, making 

 up what is commonly termed the white sub- 

 stance, are of a grey colour. Hence the only 

 valid distinction between these two kinds of 

 nervous matter, is that which has reference to 

 their constitution ; as consisting of cells or 

 vesicles on the one hand; or of tubes or fibres, 

 on the other. 



247. The connection between the fibrous and 



A small piece of the otic ganglion of 

 the sheep, slightly compressed; show- 

 ing the interlacement of the internal 

 fibres, and the vesicular matter. 

 (After Valentin.)] 



