OF THE SIMPLE FIBROUS TISSUES. 



25 



by a thin sheet of areolar tissue ; the fibres are either round or flat- 

 tened, brittle, and disposed to curl at the end. (Fig. 4.) 

 It is found in the middle coat of the arteries, in the '^" * 



chordae vocales, the ligamentum nuchas, the liga- 

 menta subflava, in the crico- thyroid membrane, and 

 in the longitudinal bands of the trachea and its 

 branches. It undergoes little or no change by boil- 

 ing, and is unaffected by acetic acid ; it resists 

 putrefaction, and preserves its elasticity during a 

 long period. 



Both these varieties may be detected in the tissue 

 now generally designated as areolar^ formerly cellu- 

 lar. This is formed by the crossing and interlacing 

 of minute fibres and bands interwoven in every di- 

 rection, so as to leave innumerable interstices which 

 communicate with each other : this may be proved 

 by filling them with air or water, as occasionally 

 happens in the living body in anasarca and traumatic 

 emphysema. (Fig. 5.) 



These interstices are not cavities possessed of definite limits, be- 

 cause they are open on all sides. The 

 application of the term cell to them, 

 is, therefore, inappropriate. The term 

 cellular is more applicable to those 

 tissues which consist of a congeries 

 of distinct cells. 



The areolar tissue is one of the most 

 extensively difTused of all the ele- 

 ments of organization, being found in 

 every part of the fabric, except in the 

 compact portion of bone, teeth, and 

 cartilage. It does not exist in the 

 brain either, except around the minute 

 vessels. Its great use is to connect 

 together organs, and parts of organs 

 whicli require a certain degree of 

 motion upon each other. To do this, 

 it is placed in their interstices, and is 

 more or less lax, and more or less abundant, according to the par- 

 ticular exigency of the part. 



It has scarcely any vital properties, but possesses the physical 

 properties of extensibility and elasticity; It has neither contracti- 

 lity nor sensibility, the nerves which it contains, being merely dis- 

 tributed in it in their route to other organs. 



Areolar tissue is readily regenerated when destroyed, and yields 

 gelatine very readily by boiling. The interstices are filled during 



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