46 THE CONNECTIVE TISSUES [CH. IV. 



respondingly diminished in quantity till in the mature cell it only forms 

 a thin film, with a flattened nucleus imbedded in its substance (fig. 66). 



Vessels and Nerves. A large number of blood-vessels are found 

 in adipose tissue, which subdivide until each lobule of fat contains 

 a fine meshwork of capillaries ensheathing each individual fat-cell 

 (fig. 68). Although nerve fibres pass through the tissue, no nerves 

 have been demonstrated to terminate in it. 



The Uses of Adipose Tissue. Among the uses of adipose tissue 

 these are the chief : 



a. It serves as a store of combustible matter which may be 

 reabsorbed into the blood when occasion requires, and, being used up 

 in the metabolism of the tissues, helps to preserve the heat of the body. 



b. The fat which is situated beneath the skin must, by its want 

 of conducting power, assist in preventing undue waste of the heat 

 of the body by escape from the surface. 



c. As a packing material, fat serves very admirably to fill up 

 spaces, to form a soft and yielding yet elastic material wherewith to 

 wrap tender and delicate structures, or form a bed with like qualities 

 on which such structures may lie, not endangered by pressure. As 

 examples of situations in which fat serves such purposes may be 

 mentioned the palms of the hands, the soles of the feet, and the orbits. 



d. In the long bones fatty tissue, in the form known as yellow 

 marrow, fills the medullary canal, and supports the small blood- 

 vessels which are distributed from it to the inner part of the substance 

 of the bone. 



Retiform Tissue. 



Eetiform or reticular tissue is a kind of connective tissue in which 

 the ground substance is of more fluid consistency than elsewhere. 



FIG. 71. Retifonn tissue from a lymphatic gland, from a section which has been treated with dilute 



potash. (Schjifer.) 



There are few or no elastic fibres in it, but the white fibres run in 

 very fine bundles forming a close network. The bundles are covered 



