CONNECTIVE TISSUE 



555 



refracting character, but the majority of them are pale 

 and not darkly contoured. All the thicker threads and 

 strings present a fine longitudinal striation as if they were 

 bundles of extremely fine fibrillte (Fig. 181, a). At intervals 

 .such bundles are often encircled by rings of a more re- 

 fractive sub.stance, and fibres of the like character may be 

 disposed spirally round the bundles. 



When dilute acetic acid is added to the specimen, the 

 pale threads and longitudinally striated strings swell up 

 and the longitudinal striation disappears : hence it is that 

 the specimen becomes so transparent (Fig. 181, b). More- 



a 



Fig. 181. 



A. A small bundle of connective tissue, showing longitudinal fibril- 

 lation, and at a and 6 encircling (annular, spiral) fibres. JIagnified 400 

 diameters. 



B. A similar bundle swollen and rendered transparent by dilute acid 

 The encircling fibres are seen at a, a, a. 



over it is these striated threads and strings which are 

 dissolved by boiling water, and yield gelatin. We may 

 therefore speak of them as collagenous or gelatin- 

 yielding fibres, by way of distinction from the fibres of 

 elastic substance, which do not yield gelatin on boiling, 

 and are of a diff'erent chemical nature. 



By various modes of maceration the collagenous fibres 

 may be resolved into filaments which answer to the space 

 between the strise, and are of such extreme fineness 

 that they may measure less than l/i in diameter. It 



