GELATINOUS TISSUE 



35 



cardium, the sclerotic coat of the eye, the fibrous sheath of the testicle, in the 

 fasciae and aponeuroses of muscles, and in the sheaths of lymphatic glands. 



Structure. To the naked eye, tendons and many of the fibrous mem- 

 branes, when in a fresh state, present an appearance as of watered silk. 

 This is due to the arrangement of the fibers in wavy parallel bundles. Under 

 the microscope the tissue appears to consist of long, often parallel, bundles 

 of fibers of different sizes. The cells in tendons, figure 39, are arranged 

 in long chains in the ground substance separating the bundles of fibers, and 

 are more or less regularly quadrilateral with large round nuclei containing 

 nucleoli, generally placed so as to be contiguous in two cells. Each of 

 these cells consists of a thick body from which processes pass in various 

 directions into, and partially fill up the spaces between, the bundles of 

 fibers. The rows of cells are separated from one another by lines of cement 

 substance. 



Yellow Elastic Tissue. Yellow elastic tissue is found chiefly in the 

 ligamentum nuchae of the ox, horse, and other animals; the ligamenta sub- 

 flava of man; the arteries, constituting the fenestrated coat of Henle; the 

 veins in the lungs and trachea; the stylo-hyoid, thyro-hyoid, and crico- 

 thyroid ligaments; in the true vocal cords; and in areolar tissue. 



Structure. Elastic tissue occurs in various forms, from a structureless, 

 elastic membrane to a tissue whose chief constituents are bundles of fibers 

 crossing each other at different angles; when seen in bundles elastic fibers are 

 yellowish in color, but individual fibers are not 

 so distinctly colored. The varieties of the tissue 

 may be classified as follows: 



a. Fine elastic fibrils, which branch and anas- 

 tomose to form a network. This variety of elastic 

 tissue occurs chiefly in the skin and mucous 

 membranes, in subcutaneous and submucous 

 tissue, in the lungs and true vocal cords. 



b. Thick fibers, sometimes cylindrical, some- 

 times flattened, which branch, anastomose and 

 form a network : these are seen most typically in 

 the ligamenta subflava and also in the ligamentum 

 nuchae of such animals as the ox and horse, in 

 which that ligament is largely developed, figure 40. 



A certain number of connective-tissue cells 

 are found in the ground substance between 

 the elastic fibers which make up this variety of 

 connective tissue, page 33. 



Areolar Tissue. This variety of fibrous tissue has a very wide dis- 

 tribution and constitutes the subcutaneous, subserous, and submucous tis- 

 sue. It is found in the mucous membranes, in the true skin, and in the outer 



FIG. 40. Elastic Fibers 

 from the Ligamenta Sub- 

 X 200. (Sharpey.) 



