CHAPTER VII. 



THE CONNECTIVE TISSUES. 

 INTRODUCTION. 



UNDER the term of 'the connective tissues,' histologists have grouped 

 together several tissues which at first would appear to have few 

 points in common to wit: connective tissue proper, including the 

 white connective tissues and yellow or elastic tissue : cartilage : bone : 

 and dentine. 



When we enquire into the grounds of this classification we 

 find that they are the following : The tissues above named are 

 derived from the same embryonic layer 1 (mesoblast) ; they all perform 

 similar, subordinate, functions of support or connection; they all 

 contain cells which develop a matrix or ground substance, which 

 has various characters in the various tissues; they shade off, as it 

 were, into one another, and represent each other in different species 

 of animals. "In one and the same organism typical development 

 brings with it a substitution of one member of the connective- 

 substance group for another. There, for instance, where in the 

 embryonic state gelatinous tissue existed, the latter is found trans- 

 formed into connective tissue or fat at a later epoch ; cartilage with 

 its derivatives takes on the form of bony substance. Finally we 

 encounter every kind of this substitution in the richest abundance, 

 brought about by the formative activity of a system modified by 

 disease. Almost every member of the group of connective tissues 

 may be replaced by very nearly any other, firstly by immediate 

 metamorphosis, then again more particularly by reconstruction from 

 the offspring of the original tissue 2 ." 



1 Tkis is not strictly true. The neuroglia, or connective tissue of the great nerve 

 centres and of the retina, is epiblastic in its origin; chemically, however, this tissue 

 differs from connective tissue, so that it is really true that true (collagenous) connective 

 tissues are derived from the mesoblast. 



3 Frey: The Histology and Histochemistry of Man, translated from the fourth 

 German edition by Arthur E. J. Barker, London, 1874, p. 167. 



