CH. IV.] 



ELASTIC AND ADIPOSE TISSUES. 



47 



Fig. 65. Transverse section of a 

 portion of lig. nuchee, show- 

 ing the outline of the fibres. 

 (After Stohr.) 





larger elastic fibres are often transversely marked, indicating their 

 mode of origin (see p. 44), and on transverse section are seen to 

 be angular (fig. 65). 



Elastic tissue, being extensible and elastic (i.e., recoiling after 

 it has been stretched), has a most important use in assisting mus- 

 cular tissue in a mechanical way, and so 

 lessening the wear and tear of such 

 an important tissue as muscle. Thus, 

 in the ligarneuta subflava of the 

 human vertebral column it assists in 

 the maintenance of the erect posture ; 

 in the ligamentum nuchse in the neck 

 of quadrupeds it assists in the raising 

 of the head and in keeping it in that 

 position. In the arterial walls, and in 

 the air tubes and lungs, it has a 

 similar important action, as we shall 

 see when discussing the subjects of 

 the circulation and respiration. 



We now come to those forms of con- 

 nective tissue in which the cells rather than the fibres are most 

 prominent. 



Adipose Tissue. 



Distribution. In almost all regions of the human body a 

 larger or smaller quantity of adipose or fatty tissue is present ; 

 the chief exceptions being the subcu- 

 taneous tissue of the eyelids, penis and 

 scrotum, the nymphee, and the cavity 

 of the cranium. Adipose tissue is also 

 absent from the substance of many 

 organs, as the lungs and liver. 



Adipose tissue is almost always 

 found seated in areolar tissue, and 

 forms in its meshes little masses of 

 unequal size and irregular shape, to 

 which the term lobules is commonly 

 applied. 



Structure. Under the microscope 

 adipose tissue is found to consist 



essentially of little vesicles or cells which present dark, sharply- 

 defined edges when viewed with transmitted light : they are 

 about ?faf or y^ of an inch in diameter ; each consists of a 

 structureless and colourless membrane or bag formed of the 



Fig. 66. Ordinary fat-cells of a 

 fat tract in the omentum of a 

 rat. (Klein.) 



