THE TISSUES 



29 



I. Formed Material. (A) Fibres (Fig. 9) 1st, Non- 

 elastic (white fibres). These are delicate, transparent fibrils 

 arranged in bundles, which do not branch, and which have 

 a mucin-like matrix between them. They are composed of 

 a non-elastic substance, collagen. This is closely allied to 

 the proteids, and gives the proteid reactions faintly, but it 

 does not yield tyrosin when decomposed, while it does yield 

 amido-acetic acid. It is insoluble in cold water, but swells 

 up and becomes transparent in acetic acid. It has a great 

 affinity for carmine, and stains a pink colour with it. When 

 boiled, it takes up water to form a hydrate, Gelatin ; a sub- 



FIG. 9. Bundles of White Fibres, with Fibroblasts (a) and Elastic Fibres (6) 

 anastomosing with one another. 



stance soluble in hot water, and forming a jelly on cooling. 

 (See Chemical Physiology, p. 7.) 



2nd, Elastic Fibres. These are highly refractile elastic 

 fibres, which branch and anastomose with one another. 

 They are composed of Elastin, a near ally of the proteids, 

 which is insoluble both in cold and in hot water, and is not 

 acted on by acetic acid. It stains yellow with picric acid, 

 and has no affinity for carmine. 



(B) Interstitial Substance. This is composed of mucus- 

 like material. 



Types of Fibrous Tissue. According to the arrangement 

 of these fibres, and to the preponderance of one or other 

 variety, various types of fibrous tissue are produced. 



