THE FIBROUS TISSUE. 149 



FIG. 2& 



The structure of this tissue is essentially fibrous, that 

 is, it consists of threads or fibres variously arranged in its 

 different divisions; some being parallel, some wavy, some 

 crossed, others mixed, and some so very compact as to 

 appear homogeneous. 



In the fibrous tissue are distinguished two kinds of fibres, 

 the white and yellow. The white (Fig. 28, A,) is described 

 as presenting the form of " inelastic bands," of variable 

 size, wavy in their direction, having numerous streaks lon- 

 gitudinally. It is reduced to gelatin by boiling, and, un- 

 der the action of acetic acid, is seen by the microscope to 

 swell up, become transparent, and exhibit oval corpuscles, 

 which latter are believed to be the formative nuclei of 

 this element. This white fibre is very abundant in tendons, 

 ligaments, fibrous membranes, aponeuroses, &c. 



The yellow fibre (Fig. 28, B,) presents the form of a cylin- 

 der; readily separates from its fellows in the longitudinal 

 direction; breaks abruptly and curls upon itself, as seen in 

 the figure, and differs from the white, in that boiling has 

 little or no effect upon it. Its elasticity is said to be pre- 

 served for an almost unlimited period. From acetic acid 

 having no effect upon it, it can always be distinguished 

 from the white tissue. Various opinions have been enter- 

 tained in reference to the ultimate structure of these fibres. 

 Mascagni believed they were absorbent vessels, surrounded 



FIG. 28. A represents the white fibrous tissue from ligament, magnified 65 

 diameters. B shows the yellow fibrous tissue from the ligamentum nuchte. 



