THE STRUCTURE OF THE ELEMENTARY TISSUES. 101 



The protoplasm of the cells is shown by various elyes itb, ]Se strfatejcf or re- 

 ticulated. The network which makes up t"His cell-body stains more 

 readily with certain dyes and is called chromophi*!i. ^ThV^^fet'^L'vfKich 

 fills in the spaces between the network of the cell-body is called the \ para- 

 plasm. The cells often contain deposits of yellowish-brown pigment 

 (tig. 105). The nucleus of the cell is sometimes reticulated. Within the 

 nucleus is sometimes seen a nucleolus, and within the nucleolus are 

 bright spots, which are known as nucleolules. 



Nerve-cells are not generally present in nerve-trunks, but are found 



\ 



Fig. 105. Cell of the anterior horn of the human spinal -cord, stained by Nissl's Method. CAfter 



Edinger.) 



in collections of nervous tissue called ganglia. They vary considerably 

 in sliape, size, and structure in different situations. 



a. Some nerve-cells are small, generally spherical or ovoid, and have 

 a regular uninterrupted outline. These single nerve-cells are most nu- 

 merous in the sympathetic ganglia ; each is inclosed in a nucleated sheath. 

 b. Others (fig. 105A) are larger, and have one, two, or more long proc- 

 esses issuing from them, the cells being called respectively unipolar, 

 bipolar, or muttipolar, which processes often divide and subdivide, and 

 appear tubular and filled with the same kind of granular material that is 

 contained within the cell. These processes are the dendrites. Generally 

 only one process from each cell is continuous with a nerve-fibre, the 

 prolongation from the cell by degrees assuming the characters of the 



