40 VETERINARY PHYSIOLOGY 



(b) Matrix. — This is composed of the mucus-Uke material 

 which is so abundant in the foetal mucoid tissue. 



According to the arrangement of the fibres, and to the 

 preponderance of one or other variety, various types of fibrous 

 tissue are produced. 



When a padding is required, as under the skin and under 

 mucous membranes, the fibres are arranged in a loose felt- 

 work to constitute areolar tissue. 



In fascia, in tendon sheaths, and in Jlat tendons, the 

 fibres are closely packed together to form more or less 

 definite layers. In tendons and ligaments the fibres run 

 parallel and close together. In the tendons of muscles, where 

 elasticity is not required, the fibres are of the white or non- 

 elastic variety. In ligaments, where elasticity is desirable, 

 the elastic fibres preponderate. 



II. The SPACES of fibrous tissue vary with the arrange- 

 ment of the fibres. In the loose areolar tissue under the 

 skin they are very large and irregular, in fascia they are 

 flattened, while in tendon, where the fibres are in parallel 

 bundles, they are long channels. 



III. The CELLS of fibrous tissue (Fibroblasts) vary greatly 

 in shape. In the young tissue they are elongated spindles, 

 from the ends of which the fibres extend. In some of the 

 loose fibrous tissues they retain this shape, but in the 

 denser tissues they get squeezed upon, and are apt to be 

 flattened and to develop processes thrust out into the 

 spaces. 



In certain situations, peculiar modifications of fibroblasts 



occur. 



(A) Endotheiium. — When these cells line the larger 

 connective tissue spaces they become flattened, and form a 

 covering resembling simple squamous epitheHum. Such a 

 layer lines all the serous cavities of the body, and the 

 lymphatics, blood-vessels, and heart, all of which are 

 primarily large connective tissue spaces. To demonstrate the 

 outlines of these cells it is necessary to stain with nitrate of 

 silver, which has a special affinity for the interstitial 



