68 NORMAL HISTOLOGY. 



VI. ADENOID TISSUE. 



Adenoid tissue consists of a network of fibrils holding in their 

 meshes lymphoid cells and leucocytes. The fibrils are supposed to 

 be derived from cell-processes, which anastomose with each other. 

 The nuclei of the cells appear at the intersections of the fibrils. It 

 occurs in lymphatic glands, tonsils, solitary glands, and Peyer's 

 patches, many mucous membranes, spleen, and thymus gland. 



VII. BASEMENT MEMBRANE, OR MEMBRANA PROPRIA. 



The basement membrane, or membrana propria, consists of a 

 delicate homogeneous membrane, composed of flattened plates of 

 cellular origin, and occurs as a supporting base for the epithelial 

 cells which line mucous membranes and the acini and ducts of 

 glands. 



VIII. CARTILAGE. 



Cartilage is a dense tissue made up of an enclosing sheath, the 

 perichondrium, a somewhat hyaline matrix, either homogeneous or 

 fibrous, and cells. 



The perichondrium is the enclosing sheath of connective tissue, 

 and consists of two layers, an outer layer of dense fibrous tissue and 

 an inner, looser layer. The terms fibrous and chondrogenetic apply 

 respectively to these layers. The latter is so called because it is 

 chiefly engaged in the formation of cartilage. It contains cells ar- 

 ranged in parallel rows, which multiply by mitosis. 



The matrix is a dense, intercellular substance of a white, bluish, 

 or yellowish color. It may be homogeneous or more or less supplied 

 with white or yellow fibres. 



Embedded in the matrix are the cartilage cells. These cells are 

 usually oval in outline, but are sometimes flattened on one side, the 

 flattened surface being toward the periphery. They are arranged 

 in pairs and groups, and are seldom crowded, except toward the 

 perichondrium. Each cell is enclosed by a capsule. The space 

 within the capsule, which is filled up by the cell, is called a lacuna. 

 There are three varieties of cartilage, determined by the presence 

 or absence of white and yellow fibres. They are hyaline cartilage, 

 elastic cartilage, and fibro-cartilage. 



