224 FIBROUS TISSUE. 



CONNECTIVE TISSUE PROPER. 



Areolar tissue. If we make a cut through the skin and proceed to raise it 

 from the subjacent parts, we observe that it is loosely connected to them by a soft 

 filamentous substance of considerable tenacity and elasticity, and having, when free 

 from fat, a white fleecy aspect ; this is the substance known as areolar tissue. In 

 like manner the areolar tissue is found underneath the serous and mucous membranes 

 which are spread over various internal surfaces, and serves to attach these membranes 

 to the parts which they line or invest ; and as under the skin it is named " sub- 

 cutaneous," so in the last-mentioned situations it is called " subserous " and " sub- 

 mucous " areolar tissue. But on proceeding further we find this substance lying 

 between the muscles, the blood-vessels, and other deep-seated parts, occupying, in 

 short, the intervals between the different organs of the body where they are not 

 otherwise insulated, and thence named " intermediate ; " very generally, also, it 

 becomes more consistent and membranous immediately around these organs, and 

 under the name of the " investing " areolar tissue, affords each of them a special 

 sheath. It thus forms inclosing sheaths for the muscles, the nerves, the blood- 

 vessels, and other parts. Whilst the areolar tissue might thus be said in some sense 

 both to connect and to insulate entire organs, it also performs the same office in 

 regard to the finer parts of which these organs are made up ; . for this end it enters 

 between the fibres of the muscles, uniting them into bundles ; it connects the several 

 membranous layers of the hollow viscera, and binds together the lobes and lobules of 

 compound glands ; it also accompanies the vessels and nerves within these organs, 

 following their branches nearly to their finest divisions, and affording them support 

 and protection. This portion of the areolar tissue has been named the " pene- 

 trating," " constituent," or " parenchymal." 



It thus appears that the areolar is one of the most general and most extensively 

 distributed of the tissues. It is, moreover, continuous throughout the body, and 

 from one region it may be traced without interruption into any other, however 

 distant ; a fact not without interest in practical medicine, seeing that in this way 

 dropsical waters, air, blood, and urine, effused into the areolar tissues, and even the 

 matter of suppuration, when not confined in an abscess, may spread far from the spot 

 where they were first introduced or deposited. 



On stretching out a portion of areolar tissue by drawing gently asunder the parts 

 between which it lies, it presents an appearance to the naked eye of a multitude of 

 fine, soft, and somewhat elastic threads, quite transparent and colourless, like spun 

 glass ; these are ! intermixed with fine transparent films, or delicate membranous 

 lamina, and both threads and laminse cross one another irregularly and in all 

 imaginable directions, leaving open interstices or areolae between them. These 

 meshes are, of course, more apparent when the tissue is thus stretched out ; it is 

 plain also that they are not closed cells, as the term " cellular tissue " which was 

 formerly used to denote the areolar tissue, might seem to imply, but merely inter- 

 spaces, which open freely into one another : many of them are occupied by the fat, 

 which, however, does not lie loose in the areolar spaces, but is enclosed in its own 

 vesicles. A small quantity of colourless transparent fluid of the nature of lymph 

 is also present in the areolar tissue, but, in health, not more than is sufficient to 

 moisten it. 



On comparing the areolar tissue of different parts, it is observed in some to be 

 more loose and open in texture, in others more dense and close, according as free 

 movement or firm connection between parts is to be provided for. 



Fibrous tissue. When the fine bundles of connective tissue are disposed for 

 the most part in one or two directions, instead of interlacing in every direction as 



