18 PTBRKH; CONNECTING TISSUE. 



being taken to cut in the direction of the fibres of the 

 latter. 



Elastic fibres are of larger size than those just de- 

 scribed ; the smallest, measure T -ro o-th of aline in breadth, 

 but they may reach ^th of a line (elastic coat of veins, 

 PI. XVI. fig. IV. 1). Their outlines are clearly 

 marked by one, and more frequently by two black 

 lines, between which is to be seen an entirely unor- 

 ganized and transparent substance. They give off 

 branches, also, in every direction, and these divisions 

 uniting again with each other, form a network of 

 variable closeness. Ordinarily, the principal branches 

 of a fasciculus of elastic fibres run parallel with each 

 other, as in the yellow elastic ligaments of the spine, 

 (PL III. fig. V. 1) ; but the secondary branches which 

 they give off present very well marked undulations, 

 and most frequently curl upon themselves. (PL III. 

 fig. V. 2 ; PL XV. fig. VI. 1.) Following this de- 

 scription it is hardly possible to confound elastic and 

 true connective fibres with each other, but we possess 

 additional means of bringing out their distinctive 

 characteristics, by the use of certain chemical reagents. 

 Thus, when we subject the connective fibre to the 

 action of acetic acid, it becomes so pale as to be unre- 

 cognisable, and finally dissolves entirely in the liquid ; 

 the same result follows, and even more rapidly, on the 

 application of diluted caustic potash. These reagents 

 produce no alteration whatever in the appearance of the 

 elastic fibres ; dilute caustic potash is even employed in 

 preparing clean and perfect specimens of them. To effect 

 this, a piece of yellow elastic ligament is to be boiled 

 for fifteen or twenty minutes in water containing some 



