ADTPOSE TISSUE. 235 



more vascular ; but the vessels seen in these membranes do not strictly belong to 

 them, being destined for the bones which they cover. 



Lymphatics are contained in great abundance, as Ludwig and Schweigger-Seidel 

 showed, in the enveloping areolar-tissue sheaths of tendons and aponeuroses, where 

 they form plexuses with polygonal meshes. In addition to these, a close network of 

 lymphatic vessels with elongated meshes may be injected in the deeper parts of the 

 tendons, where they run in the penetrating areolar tissue. Sometimes, as in the 

 central tendon of the diaphragm, lymphatic spaces separate the tendon bundles from 

 one another. A connection no doubt subsists between these lymphatics and the cell- 

 spaces of the fibrous tissue : and it has been suggested that the lymphatic vessels of 

 the tendons are partly concerned in the removal of lymph from the skeletal muscles, 

 which themselves lack true lymphatic vessels. 



The penetrating areolar tissue of tendons, like the same tissue elsewhere, possesses 

 areolse, which here take the form of elongated clefts, and these may also partly serve 

 for the passage of lymph. 



Many tendons and ligaments, and some fibrous membranes, have been shown to 

 possess nerve-fibres, which course for the most part in a direction parallel with the 

 fasciculi and may terminate in a special manner within these tissues, as will be 

 noticed when the peripheral distribution of nerves is described. 



As to elastic tissue, the yellow ligaments, which contain this in its purest form, 

 are but scantily supplied with blood-vessels, those that are present running in the 

 interstitial areolar tissue between the elastic bundles. The lymphatic vessels also 

 course for the most part longitudinally in the interstitial areolar tissue, being con- 

 nected here and there by transverse branches, and in addition to these vessels the 

 lymph may be conveyed by means of the elongated areolae of the same tissue, 

 Neither blood-vessels nor lymphatic vessels actually penetrate into the small bundles 

 of elastic fibres, although the lymphatic vessels often lie close against the surface of 

 the bundles. 



ADIPOSE TISSUE. 



The human body in the healthy state contains a considerable amount of fatty 

 matter of different kinds. It exists in several of the secretions in some constitu- 

 ting the chief ingredient ; and it enters into the composition of many of the 

 textures. But by far the greater part of the fat of the body is inclosed in cells of 

 the areolar tissue, which, together with the fibres and blood-vessels which pass 

 between them and serve to bind them together, constitute the adipose tissue. 



Distribution. This tissue is not confined to any one region or organ, but 

 exists very generally throughout the body, accompanying the still more widely dis- 

 tributed areolar tissue in most, though not in all parts in which the latter is found. 

 Still its distribution is not uniform, and there are certain situations in which it is 

 collected more abundantly. It forms a considerable layer underneath the skin, and, 

 together with the subcutaneous areolar tissue in which it is lodged, constitutes in 

 this situation what has been called the panniculns adiposus. It is collected in large 

 quantity round certain internal parts, especially the kidneys. It is seen filling up 

 the furrows on the surface of the heart, and imbedding the vessels of that organ 

 beneath its serous covering ; and in various other situations it is deposited beneath 

 the serous membranes, or is collected between their folds, as in the mesentery and 

 omentum, at first generally gathering along the course of the blood-vessels and at 

 length accumulating very copiously. Collections of fat are also common round the 

 joints, lying on the outer surface of the synovial membrane, and filling up in- 

 equalities ; in many cases lodged in folds of the membrane, which project into the 

 articular cavity. Lastly, the fat exists in large quantity in the marrow of bones. 



VOL. i. R 



