ELASTIC TISSUE 



415 



The movements of cilia, like those observed in fully-developed 

 spermatozoids, seem to be independent of nervous influence, and they 

 are affected only by local conditions. They may continue, under favor- 

 able circumstances, for more than twenty-four hours after death, and 

 they can be seen in cells detached from the body, when moistened with 

 proper solutions. When the cells are moistened with water, the activ- 

 ity of their movement is at first increased ; but it soon disappears as the 

 cells become swollen. Acids arrest the movements, but they may be 

 excited by feebly alkaline solutions. As regards the uses of these move- 

 ments, it is sufficient to refer to the physiology of the parts in which 

 cilia are found, where the peculiarities of their action are considered 

 more in detail. In the lungs and the air-passages generally and in the 

 genital passages of the female, the currents are of 

 considerable importance ; but it is difficult to imagine 

 the use of these movements in certain other situa- 

 tions, as the ventricles of the brain. 



Movements due to Elasticity. There are certain 

 important movements in the body due simply to the 

 action of elastic ligaments or membranes. These are 

 distinct from muscular movements and are not to be 

 classed even with the movements produced by the 

 resiliency of muscular tissue, in which muscular to- 

 nicity is more or less involved. Movements of this 

 kind consist simply in the return of movable parts to 

 a certain position after they have been displaced by 

 muscular action, and in the reaction of tubes after Fig< 8l _ White 

 forcible distention, as in the walls of the large arteries, fibrous tissue; one end 



. . of the bundle has been 



Elastic FlSSlie. Most anatomists adopt the dlVl- teased out so as to display- 



sion of the fibres of elastic tissue into three varieties. th ^^ nent fibrill(S 

 This division relates to the size of the fibres ; and all 

 varieties are found to possess essentially the same chemical composition 

 and general properties. On account of the yellow color of this tissue, 

 presenting, as it does, a decided contrast to the white glistening appear- 

 ance of the inelastic fibres, it frequently is called the yellow elastic 

 tissue. 



The first variety of elastic tissue is composed of small fibres, usually 

 intermingled with fibres of the ordinary inelastic tissue. They possess 

 all the chemical and physical characters of the larger fibres but are 

 very fine, measuring ^^ to ^ir or innnr of an inch (i to 4 or 5 /*) in 

 diameter. If acetic acid is added to a preparation of ordinary connec- 

 tive tissue, the inelastic fibres are rendered semitransparent, but the 

 elastic fibres are unaffected and become quite distinct. They are then 



