CONNECTIVE TISSUE. 



55 



placing a lump of warm, soft wax between the points of 

 three fingers and pressing them together. 



There is still another cell formation met with in connective- 

 tissue structures ; they are often very rare ; in places, how- 

 ever, quite numerous. They are larger, coarse granular 

 structures, with a nucleus and an either rounded or spindle- 

 shaped body, without that system of lamellae and processes 

 of the previous form (b). They have been met with in the 

 vicinity of vessels, especially arteries, and have received the 

 name of plasma cells (Waldeyer). 



Fat cells may proceed from both varieties of cells, the flat 

 and the coarse granular (p. 49). 



Connective-tissue cells also assume an extremely peculiar 

 appearance from receiving melanine granules into their body 

 (Fig- 9). This is the "stellate pigment cell" of the earlier 

 histolomsts. The coal or brown- black molecules are smaller 

 than in the pigmented epithelium (p. 30). In man such cells 

 are limited almost exclusively to the eye. In the lower ver- 

 tebrates, such as many of the amphibia, this process of pig- 

 ment embedding is enormously diffused, so that in every little 

 piece of connective tissue the strangest cells are met with, 

 occurring in every possible stellate form. 



The fiat connective-tissue cells and their colored associates 

 (Fig. 56), show a slow, 

 but unmistakable vital 

 contractile power. This 

 is not yet recognized in 

 the plasma cell. 



Connective tissue, whose 

 immense diffusion in the 

 human body we have al- 

 ready mentioned, by the 

 arrangement and interlac- 

 ing of its bundles, by its 

 very dissimilar proportion of elastic elements, the extremely 

 variable vascularity, and, finally, by the commingling of insol- 

 uble elements, forms substances which appear to the naked 



Fig. 56. — Gradual change of form of a pigmented 

 connective-tissue corpuscle from a water newt, during 

 45 minutes. 



