CHAP. VI I.I THE CONNECTIVE TISSUES. 251 



Connective Tissue Cells. 



These are the anatomical elements which are alone present in 

 the earliest stages of the development of connective tissue ; and it is 

 probably by the differentiation of their protoplasm that the inter- 

 cellular structures are ultimately formed which give to 'the different 

 varieties their peculiar characters. 



We must refer the reader to works on Histology for a full 

 description of the various forms of connective tissue cells. We shall 

 in this place confine ourselves to the following categorical statements. 



(1) Connective tissue cells consist invariably of a more or less 

 finely granular and contractile protoplasm, in which lies imbedded a 

 nucleus (sometimes more than one), usually of a vesicular nature. 

 The connective tissue cell, whilst it is in its state of typical activity, 

 is destitute of a cell wall, though occasionally one may be developed 

 (as in the fat cell) by the differentiation of the peripheral portion of 

 the cell-protoplasm. In certain cases branching processes are given 

 off from the protoplasm of the connective tissue cells and may serve 

 to connect adjoining cells together. 



(2) In certain regions connective tissue cells are found (e.g. in 

 the cornea) imbedded in cavities in the ground substance; these 

 cavities sometimes communicate by minute canals, so that there is 

 established a canal system through which liquids may permeate 

 (Saftcanalchensystem). Such spaces or cavities are in certain 

 situations doubtless continuous with the smallest lymphatic vessels. 



(3) In other situations the cells are discontinuous and resemble 

 rows of cells laid against the bundles of white fibres, one row to 

 each small bundle : being connected to them, and supported, by the 

 ground substance or matrix. 



(4) In some situations pigment is deposited in the protoplasm of 

 the connective tissue cells (e.g. in the outer layer of the choroid) ; 

 in others, fat is formed at the expense of the protoplasm. 



(5) Lastly, there occur in the connective tissues certain cells, which 

 are in all respects similar to the colourless cells of the blood, and 

 which wander through the connective tissue spaces, in virtue of the 

 amoeboid movements with which they are endowed. These are, 

 doubtless, either colourless cells of the blood which have passed 

 through the capillary walls, or they are the offspring of cells which 

 have thus emigrated. 



Micro-Che- ^ ur m f rm ation in reference to the chemistry of 



micaireac- the connective tissue cell is, necessarily, of the most 

 tions of the limited character and is almost confined to a knowledge 

 connective that the protoplasm is proteid in nature and that the 

 nucleus shares the characters of nuclei elsewhere and 

 has probably the same composition. 



It may be convenient however to summarize the effects of certain 

 reagents upon these cells. 



