RETICULAR TISSUE 



6l 



fluid intercellular substance (Fig. 50). The protoplasmic processes of 

 the primitive mesenchyma have become transformed into flattened strands 

 or slender fibers, which are clear and homogeneous, and anastomose 

 freely. The cells associated with these fibers contain pale, flattened, 

 oval nuclei, with few chromatin granules. In ordinary sections reticular 

 tissue will be most readily recognized by the cells lodged in the fluid in- 

 tercellular substance. These cells, which are chiefly lymphocytes, having 

 round nuclei and a narrow rim of protoplasm, are often so abundant that 

 the tissue appears as a dense cellular mass in which the framework of 

 reticular tissue is almost completely hidden. Upon careful examination, 

 however, some of its nuclei and fibers can always be detected. 



a 



FIG. 50. RETICULAR TISSUE SEEN IN A FROZEN SECTION OF A DOG'S SPLEEN WHCIH HAD BEEN INJECTED 

 WITH SILVER NITRATE. Xzso. (Mall.) 

 A, artery with its ampullae (a) : V, vein. 



In order to study reticular tissue advantageously, the lymphocytes 

 and other forms of free cells should be disengaged from its meshes. This 

 may be accomplished by shaking or brushing the sections; or by arti- 

 ficially digesting the specimen (which if properly done will destroy the 

 cells, including those of the reticular tissue, but will leave the network 

 of fibers); or by the following ingenious method devised by Mall. A 

 piece of fresh spleen is distended by injecting gelatin into its substance; 

 it is then frozen and sectioned. The sections are put in warm water, which 

 dissolves out the gelatin, carrying the loose, cells with it, and leaves areas of 

 clear reticular tissue. Professor. Mall has also shown how to wash out the 



