34 THE CONNECTIVE TISSUES [CH. IY. 



Under the microscope each lobule is found to consist of little 

 vesicles or cells which present dark, sharply-defined edges when 

 viewed with transmitted light: they are about ^^ or -^J-g- of an 

 inch in diameter; each consists of a structureless and colourless 

 membrane or bag formed of the remains of the original protoplasm 

 of the cell, filled with fatty matter, which is liquid during life, but 

 is in part solidified (or sometimes crystallised) after death. A 

 nucleus is always present in some part or other of the cell proto- 

 plasm, but it is not easily visible unless the tissue is stained. 



The oily matter contained in the cells is composed of the com- 

 pounds of fatty acids with glycerin, which are named olein, stearin, 

 and palmitin. On the addition of osmic acid, fat-cells are stained 

 black; this is due to the olein present, which reduces the osmium 

 tetroxide to a lower oxide, which has a black colour. Fat is 

 stained deep yellow by Sudan III. and red by Scharlach R 



Fat-cells are developed from connective-tissue corpuscles; these 

 colls may be found exhibiting every intermediate gradation between 



an ordinary corpuscle and a mature fat- 

 cell. The process of development is as 

 follows: a few small drops of oil make 

 their appearance in the protoplasm, and 

 by their confluence a larger drop is 

 produced: this gradually increases in size 

 at the expense of the original protoplasm 

 of the cell, which becomes correspondingly 

 diminished in quantity till in the mature 

 cell it only forms a thin film, with a 

 ,FIO. 47. Fat-ceiis from the flattened nucleus imbedded in its substance 



omentum of a rat. (Klein.) /r> .^ , . L_. 



(figs. 41 and 47). 



A large number of blood-vessels are found in adipose tissue, which 

 subdivide until each lobule of fat contains a fine meshwork of capil- 

 laries enshea thing each individual fat-cell. 



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 



