SECT. 124.] NERVOUS SYSTEM. 1$$ 



themselves to this effect. Sometimes these fibres are more 

 readily separated, sometimes they are united into a more compact 

 substance similar to homogeneous connective tissue. In the for- 

 mer case, they appear as flat, pale fibres, 0-0015'" to 0-0025'" in 

 breadth, o'ooo6'" in thickness, with indistinctly striated, more 

 granular or homogeneous substance, presenting the same reaction 

 with diluted organic acids as areolar tissue, and possess, from 

 place to place, mostly elongated or fusiform nuclei, 0-003'" to 

 0'007'" long, 0-002'" to 0-003'" broad. These fibres, which, in 

 certain places, anastomose like reticulate areolar tissue, are found 

 in all the grey parts of the ganglionic nerves in very large numbers, 

 so that they outnumber the dark -bordered genuine nerve-tubes 

 3 to 1 o times and more. They mostly constitute the proper matrix 

 of these cords (fig. 106), and then, the dark-bordered tubes extend 

 through the midst of them, sometimes more isolated, sometimes 

 in larger and smaller bundles. More rarely, and only in the 

 neighbourhood of and in the ganglia themselves, they appear as 

 investments of certain of the finest tubes. Besides the presence 

 of these fibres of Remak, the peripheral distribution of the sym- 

 pathetic is especially characterised by the occurrence of a large 

 number of ganglia. They are larger or smaller, or even micro- 

 scopical in size, and are situated upon the trunks or termination 

 of the nerves. The smallest or microscopical, so far as is hitherto 

 known, exist upon the nervi carotid, in the pharyngeal plexus, in 

 the heart, at the root of the lungs, and in the lungs, occasionally 

 upon the posterior wall of the urinary bladder, on the muscular 

 substance of the neck of the uterus of the pig, and in the plexus 

 cavernosi. Their distribution will be considered more in detail 

 when treating of the viscera ; I will here only remark in general, 

 that, in what regards the size and form of the ganglion-cells and 

 the origin of the fine fibres, they present exactly the same relations 

 as the ganglia of the sympathetic cord. With reference to the 

 latter point, it may be particularly mentioned, that the origin of 

 nerve-fibres from unipolar cells, and the rarity of the double origin 

 of fibres may be especially well seen in one place, namely, in the 

 septum of the heart of the frog, where also R. Wagner admits 

 the fact. Accordingly, these ganglia are also sources of nerve- 

 fibres, and the branches passing out of them are always richer in 

 tubes than the roots, provided the fibres pass out only in one 

 direction, which is, perhaps, the case in most places. Here also 

 may most readily convince ourselves that there are many apolar 

 cells without 'processes, as is most plainly shown in the heart- 



