STRUCTURE OF THE NERVE-CEXTRES. 45 



beneath the epithelium, coming from a submucous plexus 

 analogous to the deep cutaneous plexus. In certain mem- 

 branes, we have already noted the termination in bulbs (cor- 

 puscles of Krause). In the cornea the fibres have been fol- 

 lowed more minutely than in any other situation, and the 

 results of recent researches on this subject are very remark- 

 able. These results are so recent and unexpected, that we 

 are hardly prepared to admit them unreservedly without 

 fuller confirmation. At present we can only state that the 

 observations of Hoyer, 1 Lipmann, 2 and others, confirmed in 

 part by Kolliker, 8 seem to show that branching nerve-fibres 

 pass to the nucleoli of the corpuscles of the cornea and to the 

 nucleoli of the cells of the posterior layer of epithelium. 



Structure of the Neme-centres. 



A peculiar pigmentary matter in the nerve-cells and the 

 surrounding granular substance gives to the nerve-centres 

 a grayish color, by which they are readily distinguished 

 from the white, or fibrous division of the nervous system. 

 Wherever this gray matter is found, the anatomical ele- 

 ments of the tissue are cellular, except in the nerves formed 

 of gray, or gelatinous fibres. Under the general division of 

 nerve-centres, we include, anatomically at least, the gray 

 matter of the cerebro-spinal centres, the ganglia of the roots 

 of the spinal and certain of the cranial nerves, and the nu- 

 merous ganglia of the sympathetic system. In these parts 

 are found cells, which constitute the essential anatomical 

 element of the tissue, granular matter resembling the con- 

 tents of the cells, pale fibres originating in prolongations of 

 the cells, elements of connective tissue, delicate membranes 



1 HOYER, Ueber den Amtritt von Nervenfaser in das Epithel der Hornhaut. 

 Archiv fur Anatomie, Physiologie und wissenschaftliche ATedicin, Leipzig, 1866, 

 S. 180, et seq. 



2 LIPPMAXN, Ueber die Endigung den Nerven im eigentlichen Gewebe nnd im 

 kinterea Epithel der Hornhaut des Frosches. ArchivfUr Pathologic, Anatomie und 

 Physiologie, Berlin, 1869, Bd. xlviii., S. 218, et seq. 



3 KOLLIKER, fitments d'histologie humaine, Paris, 1868, p. 145. 



