THE CONNECTIVE TISSUES. 



1091 



removed or brushed away before the fibres become visible. In many situations 

 the interstices of the network are filled with rounded lymph-corpuscles, and the 

 tissue is then termed lymphoid or adenoid tissue (Fig. 616). 



3. Basement-membranes, formerly described as homogeneous membranes, are 

 really a form of connective tissue. They constitute the supporting membrane, 



FIG. 617. Adipose tissue. High power, a, Star-like appearance from crystallization of fatty acids. 



or membrana propria, on which is placed the epithelium of mucous membranes or 

 secreting glands, and in other situations. By means of staining with nitrate of 

 silver they may be shown to consist of flattened cells in close opposition, and 

 joined together by their edges, thus 

 forming an example of an epithelioid 

 arrangement of connective-tissue cells. 

 In some situations the cells, instead 

 of adhering by their edges, give off 

 branching processes, which join with 

 similar processes of other cells, and 

 so form a network rather than a con- 

 tinuous membrane. In other instances 

 basement-membranes are* composed of 

 elastic tissue, as in the cornea, or, 

 again, in other cases of condensed 

 ground-substance. 



Adipose Tissue. In almost all 

 parts of the body the ordinary areolar 

 tissue contains a variable quantity of 

 fat. The principal situations where 

 it is not found are the subcutaneous 

 tissue of the eyelids, the penis and 

 scrotum, the nymphse, within the 

 cavity of the cranium, and in the 

 lungs, except near their roots. Nevertheless, its distribution is not uniform : in 

 some parts it is collected in great abundance, as in the subcutaneous tissue, espe- 

 cially of the abdomen ; around the kidneys; on the surface of the heart between 

 the furrows ; and in some other situations. Lastly, fat enters largely into the 

 formation of the marrow of bones. A distinction must be made between fat and 

 adipose tissue; the latter being a distinct issue, the former an oily matter, which 

 in addition to forming adipose tissue is also widely present in the body, as in the 

 fat of the brain and liver, and in the blood and chyle, etc. 



Adipose tissue consists of small vesicles, fat-cells, lodged in the meshes of 

 areolar tissue. The fat-cells (Fig. 617) vary in size, but of about the average 



FIG. 618. Development of fat. (Klein and Noble 

 Smith.) a. Minute artery, v, Minute vein, c, Capillary 

 elood-vcssls in the course of formation; they are not 

 yet completely hollowed out, there being still left in 

 them protoplasmic septa, d. The ground-substance, con- 

 taining numerous nucleated cells, some of which are 

 more distinctly branched and flattened than others, and 

 appear therefo're more spindle-shaped. 



