THE STRUCTURE OF THE ELEMENTARY TISSUES. 



33 



rally marked by one or more lines or stripes when viewed longitudi- 

 nally. This appearance is really produced by the laminar extension 

 either projecting upwards or downwards. 



FIG. 33. A. Mature white fibrous tissue of 

 tendon, consisting mainly of fibres with a few 

 scattered fusiform cells. (Strieker.) 



FIG. 34. Caudal tendon of young rat, 

 showing the arrangement, form, and struc- 

 ture of the tendon cells, x 300. (Klein.) 



The branched character of the cells is seen in transverse section in 

 Fig. 35. 



(b.) Yellow Elastic Tissue. 



Distribution. In the ligamentum nuchae of the ox, horse, and many 

 other animals; in the ligamenta subflava of man; in the arteries, con- 

 stituting the fenestrated coat of Henle; in veins; in the lungs and 

 trachea; in 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 structure- 

 less, elastic membrane to a tissue whose chief constituents are bundles 

 of fibres, crossing each other at different angles; when seen in bundles 

 elastic fibres are yellowish in color, but individual fibres are not so dis- 

 tinctly colored. The varieties of the tissue may be classified as follows: 



(a.) Fine elastic fibrils, which branch and anastomose to form a net- 

 work; 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 fibres, sometimes cylindrical, sometimes flattened like 

 tape, 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 it is largely devel- 

 oped (Fig. 32). 



(c.) Elastic membranes with perforations, e. g., Henle's fenestrated 

 membrane: this variety is found chiefly in the arteries and veins. 



(d.) Continuous, homogeneous elastic membranes, e. g., Bowman's 

 3 



