GANGLION-GLOBULES. J 



a protecting investment of fibres resembling areolar tissue to 

 both structures. This is certainly a very striking comparison, 

 but the external investment must not in either instance be re- 

 garded as a something unessential, as a structure composed of 

 other elementary parts, for the ganglion-globules, like the yelk, 

 are true cells, and their external covering is an essential com- 

 ponent part of them ; it is the cell-membrane. The vitelline 

 membrane of the bird's egg, while contained in the ovary, 

 is perfectly structureless, not composed of more minute ele- 

 mentary parts ; the same is the case with the investment of the 

 ganglion-globules. They are both of them true simple cells. 

 The parenchyma of the ganglion-globules forms the cell-con- 

 tents, and the vesicle in their interior is the cell-nucleus ; the 

 small corpuscles which it contains are the nucleoli. The vesicle 

 of the ganglion-globules lies, as in other cells, eccentrically 

 upon the internal surface of the cell-membrane. This cell- 

 membrane may be most distinctly observed in the ganglion- 

 globules of the sympathetic nerves of the frog, previous to their 

 junction with the sacral plexus. (See pi. IV, fig. 10, a.) Tt there 

 appears comparatively dark, and sharply defined, both externally 

 and internally, so that its thickness may be readily measured. 

 Valentin has already remarked, that the capsule of the gan- 

 glion-globules is thicker in the lower animals. In the situation 

 before mentioned in the frog, it seems as though a ganglion- 

 globule were sometimes formed within another cell. (See fig. 

 10, b.) The ordinary contents of these ganglion- globules ^is a 

 minutely-granulous, yellowish substance. On one occasion, 

 however, I saw a ganglion-globule from the head of an ox (I 

 do not precisely know from what part it was taken), in which 

 the granulous appearance was confined to the surface, the inte- 

 rior being clear, — a fact which was rendered distinctly percepti- 

 ble by causing the globule to roll about, It is nothing remarkable 

 that two nuclei should sometimes occur in one ganglion-glo- 

 bule ; we have observed this already in several cells, in those 

 of cartilage for instance. In those instances, however, only 

 one of them was the true cell-nucleus, the cytoblast of the car- 

 tilage-cell, the other being a subsequent formation within the 

 cell. 



