16 ANATOMY FOE, NUKSES. [CHAP. III. 



sinews or tendons, by means of which the muscles are attached 

 to the bones. It also forms fibrous membranes which invest 

 and protect different parts or organs of the body. Examples 

 of these are seen in the periosteum and perichondrium, which 

 cover the bones and cartilages, and in the dura mater, which 

 lines the skull and protects the brain. Fibrous membranes, 

 called fascice, are also employed to envelop and bind down the 

 muscles of different regions, of which the great fascia enclosing 

 the muscles of the thigh and leg is a well-known example; 

 and, under the name of aponeuroses, serve for the attachment of 

 muscles in various parts of the body. It thus appears that 

 fibrous tissue presents itself in the form of strong bands or 

 cords, and of dense sheets or membranes. 



Fibrous tissue is white, with a peculiarly shining silvery 

 aspect. It is exceedingly strong and tough, yet perfectly 

 pliant ; but it is almost devoid of extensibility. By these qual- 

 ities it is admirably suited to the purposes for which it is used 

 in the human frame. By its inextensile character, and by its 

 strength, it maintains in apposition the parts which it connects, 

 and we find that the ligaments and tendons do not sensibly 

 yield to extension in the strongest muscular efforts ; and though 

 they sometimes snap asunder, it is well known that bones will 

 break more readily than ligaments ; and the fibrous membranes 

 or aponeuroses are equally strong, tough, and unyielding. 



Elastic tissue. In elastic tissue the wavy white bundles are 

 comparatively few and indistinct, and there is a proportionate 

 development of the elastic fibres. When present in large num- 

 bers they give a yellowish colour to the tissue. This form of 

 connective tissue is extensile and elastic in the highest degree, 

 but is not so strong as the fibrous variety, and breaks across the 

 direction of its fibres when forcibly stretched. 



It occurs in its most characteristic form in what is called 

 the ligamenta subflava, which forms an elastic band between 

 some of the bones of the spine. Elastic tissue is also found in 

 the walls of the air tubes and in the vocal cords ; it unites the 

 cartilages of the larynx ; and enters largely into the formation 

 of the walls of the blood-vessels, especially of the arteries. 



These three varieties of connective tissue agree closely with 

 one another in elementary structure. It is the different ar- 

 rangement of the cells and fibres, and the relative proportion of 



