b:x AREOLAR TISSUE. 



"reticular" tissue; it used formerly to be commonly called "cellular 

 membrane." In like manner the areolar tissue is found underneath the 

 serous and mucous membranes which are spread over various internal sur- 

 faces, and serves to attach those membranes to the parts which they line or 

 invest ; and as under the skin it is named "subcutaneous," so in the last- 

 mentioned situations it is called "subserous" and "submucous" 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 

 many 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 " penetrating," " 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 through- 

 out 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 tissue, 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 elastic threads, quite transparent and colourless, 

 like spun glass ; these are intermixed with fine transparent films, or 

 delicate membranous laminae, and both threads and laminae cross one 

 another irregularly and in all imaginable directions, leaving open interstices 

 or areolse 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 " might seem to imply, but merely inter- 

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

 the fat, which, however, as already explained, does not lie loose in the 

 areolar spaces, but is enclosed in its own vesicles. A small quantity of 

 colourless transparent fluid is also present in the areolar tissue, but, in 

 health, not more than is sufficient to moisten it. This fluid is generally 

 said to be of the nature of serum ; but it is not improbable that, unless 

 when unduly increased in quantity or altered in nature by disease, it may 

 resemble more the liquor sanguinis, as is the case with the fluid of most of 

 the serous membranes. 



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 pro- 

 vided for. In some situations, too, the laminae are more numerous ; in 



