TISSUES OF THE BODY. 



219 



o 



Fig. 212. A portion of a human sympathetic 

 ganglion. A, four ganglion cells surrounded 

 by homogeneous nucleated connective-tis- 

 jue; a, without a nucleus; c, containing 

 two of the latter. This tissue, b 6, passes off 

 into the fibres d d. It, & cell without an 

 envelope. 



find connective-tissue corpuscles, until, finally, in tlie larger nervous trunks, 



the perineurium assumes an exquisitely fibrillated character, and discloses 



a rich network of elastic fibres. 



Further, a similar homogeneous nucleated tissue encloses, as an external 



capsule, the nerve-cells in the ganglia (fig. 212, A}. Not unfrequently we 



have opportunity of remarking how, from 



this connective-tissue acting thus as an 



envelope to the cells, flat bands pass off 



(d d). There is a pressing necessity here. 



however, for closer investigation. 



Later on we shall have to inquire into 



the nature of the so-called fibres of 



Remalc, in considering the nervous 



system, pale nucleated threads of mixed 



nature. Some structures described as 



such appear to belong to the connective- 

 tissues, and to be a species of the latter 



similar to that of the envelopes of the 

 ganglion cells just mentioned. 



We meet with very peculiar masses of 

 connective-substance in certain tissues of 

 the body of vertebrate animals, in which 

 (like many of the flat epithelia, 89) 

 the cells are filled with granules of black 

 or the nearly allied broicn pigment. 

 The particles of this melanin, however, are smaller than those in the epithe- 

 lial cells. 



Connective-tissue corpuscles of this kind, the stellate pigment cells of 

 an earlier epoch (fig. 213), are found in the human body almost ex- 

 clusively confined to the eye. Among the 

 lower vertebrates, however, they may attain 

 an enormously wide distribution through- 

 out the body, so that we encounter them in 

 all parts formed of connective-tissue, for 

 instance, in the frog. 



In these vital contractility has been 

 observed, and the power of wandering from 

 one situation to another. Thus they may 

 penetrate from the connective-tissue be- 

 tween the cells of the epidermis, by virtue Fig 213 

 of this power. 



Fig. 214 represents the changes of form 

 in one of these migrating cells. 



In the human eye, the number of melanin cells of this kind is either 

 very considerable, while the proportion of intermediate matter is mode- 

 rate (the latter being at the same time homogeneous more or less), or the 

 cells occur more isolated amid fibrous typical connective-tissue. 



A case of the first kind is to be found in the choroid. In it we encounter 

 a dense network of these cells, of stellate or fusiform figure, with oval 

 nuclei, and a varying number of processes, which elongate themselves 

 frequently into extremely thin filaments, appearing at times tangled : 

 through these the cells are connected with one another. The size of the 

 latter is about '0226-0 '0452 mm. Altogether this reminds us of the 



-Pigmentary connective-tissue 

 corpuscles (so-called stellate pigment 

 cells), from the lamina fusca of the 

 mammal eye. 



