STRUCTURE OF THE ELEMENTARY TISSUES. 



33 



elastic fibres crossing each other at different angles: these varieties 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 and form a network: these are 'seen most typically in the 

 ligcimenta subflava and also in the ligamentum nuchae of such animals as 

 the ox and horse, in which it is largely developed. 



(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 



FIG. 31. FIG. 32. 



FIG. 31. Tissue of the jelly of Wharton from umbilical cord. a. connective-tissue corpuscles; 

 b. fasciculi of connective tissue; c. spherical formative cells. (Frey.) 



FIG. 32. Part of a section of a lymphatic gland, from which the corpuscles have been for the 

 most part removed, showing the adenoid recticulum. (Klein and Noble Smith.) 



anterior elastic lamina, and Descemet's posterior elastic lamina, both in 

 the cornea. 



A certain number of flat connective tissue cells are found in the 

 ground substance between the elastic fibres constituting this variety of 

 connective tissue. 



B. Special Forms. (a.) Gelatinous Tissue. 



Distribution. Gelatinous connective tissue forms the chief part of 

 the bodies of jelly fish; it is found in many parts of the human embryo, 

 but remains in the adult only in the vitreous humor of the eye. ' It may 

 be best seen in the last-named situation, in the "Whartonian jelly" of the 

 umbilical cord, and in the enamel organ of developing teeth. 

 VOL. I. 3. 



