CONNECTIVE TISSUES 159 



to support, strengthen and bind together the various organs 

 and parts of the body. Histologically the connective tissues 

 consist of elements of four kinds, united together in very 

 varying proportions in different situations : (1) white fibrous 

 tissue , (2) yellow elastic tissue ; (3) connective tissue cor- 

 puscles, which are comparatively slightly altered cells, usually 

 branched ; and (4) ground substance, or intercellular sub- 

 stance. 



I. White Fibrous Tissue. This consists of a number of 



fine transparent fibres of a more or less cylindrical 

 shape, and with a very characteristic wavy outline ; 

 between the fibres are connective tissue cells, usually 

 in small numbers. The fibres are arranged side by 

 side in bundles, and each fibre presents a number of 

 longitudinal fibrillar striations. The cellular origin 

 of white fibrous tissue is difficult to determine. The 

 fibres are believed to be formed by modification of the 

 intercellular matrix rather than from the bodies of 

 the cells themselves. 



a. Tendon of rat's tail. Pull out a small piece of ten- 

 don from the tail of a rett-; place it on a slide 

 in a drop of normal salt solution; spread it out 

 with needles, cover and examine with low and high 

 powers : note : 



i. The fibres, with wavy outlines. 



ii. The fibrillae, indicated by longitudinal wavy stria- 

 tions within the fibres. 



Add a drop of acetic acid to the preparation : note that 

 iii. The fibres swell up and become transparent. 



iv. Longitudinal rows of tendon cells, with nuclei, 

 become visible between the fibres. 



II. Yellow Elastic Tissue. This consists' of fine branching 



homogeneous fibres, with great power of resisting 



