SIMPLE FIBROUS TISSUES; AREOLAR TISSUE. 121 



tamorphosis of cells, their origin being rather, it seems more probable, in the 

 fluid blastema ( 136). The interstices of Areolar tissue are tilled during life 

 with a fluid, which resembles a very dilute Serum of the blood ; it consists 

 chiefly of water, but contains a sensible quantity of common salt and albumen, 

 and (when concentrated) a trace of alkali sufficient to affect test-paper. The pre- 

 sence of this fluid seems to result from an act of simple physical transudation; 

 for it has been found that, when the serum of the blood is made to percolate 

 through thin animal membranes, the water charged with saline matter passes 

 through them much more readily than the albumen, a part of which is kept 

 back. 



139. The great use of Areolar tissue appears to be, to connect together 

 organs and parts of organs, which require a certain degree of motion upon 

 one another : and to envelope, fix, and protect, the blood-vessels, nerves, and 

 lymphatics with which these organs are to be supplied. It can scarcely be 

 said to enjoy any vital powers, and is connected solely with physical actions 

 ( 134). It is extensible in all directions, and very elastic, in virtue of the 

 physical arrangement of its elements ; and it possesses no contractility, be- 

 yond that of the vessels which are distributed through it. It cannot be said 

 to be endowed with sensibility ; for the nerves which it contains seem to be 

 merely en route to other organs, and not to be distributed to its own elements. 

 And its asserted powers of absorption and secretion appertain rather to the 

 walls of the capillary blood-vessels, than to the threads and bands of which 

 it is composed. It is regenerated more readily than any other tissue, save 

 the Epithelium; being produced, it would appear, by the simple consolida- 

 tion of the blastema, that is poured out (in the form of organizable lymph) in 

 situations where there has been a breach of substance. It is also formed in 

 the effusions of a similar fluid, which are deposited on the surfaces, or in 

 the substance, of inflamed tissues. Areolar tissue yields Gelatine by boiling ; 

 but this is derived from the White Fibrous element only ; the Yellow not 

 being affected by the process. 



140. The White Fibrous tissue exists alone in Ligaments, Tendons, Fi- 

 brous Membranes, Aponeuroses, &c. ; where it presents the same characters 

 as those just described, except that the bands are less wavy, and frequently 

 quite straight, so that it is inextensible. It receives very few blood-vessels, 

 and still fewer nerves ; indeed it would seem that, in many structures (as ten- 

 dons), it is totally insensible. It seems entirely destitute of any vital pro- 

 perty ; and its chemical nature is such, that it needs very little interstitial 

 change to maintain its normal composition. If dried, it has not the least tend- 

 ency to putrefy ; and when moist, it resists the putrefactive process more 

 strongly than almost any of the softer textures. The peculiar and important 

 property of this tissue, is its capability of resisting extension ; and we find it 

 in situations, where a firm resistance is to be made to traction. If the traction 

 be applicable in one direction only, as in Tendons and most Ligaments, we 

 find the bundles of fibres or bands arranged side by side ; but if it be exerted in 

 various directions, the fasciculi cross one another, as in Fibrous Membranes. 

 The reparation of this tissue is effected by the interposition of a new substance, 

 every way similar to the original, except that it wants its peculiar glistening 

 aspect, and is more bulky and transparent. The Yellow Fibrous tissue exists 

 separately in the middle coat of the Arteries, the Chorda? Vocales, the Liga- 

 mentum Nuchse (of quadrupeds) and the Ligamenta subflava ; and it enters 

 largely into the composition of some other parts. It differs remarkably from 

 the white, in the possession of a high degree of elasticity ; so that the tissues, 

 which are composed of it alone, are among the most elastic of all known sub- 

 stances. It is, however, much more brittle than the white ; and its fibres 

 usually exhibit a marked tendency to curl at their broken ends. Their size 



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