FIBROUS TISSUE. Ixxv 



true, when the extending force acts slowly and for a long time, as when 

 tumours or fluids slowly gather beneath them ; but perhaps this gradual 

 extension is accompanied with some nutritive change affecting the properties 

 of the tissue. 



Structure. The fibrous tissue id made up of fine filaments, agreeing in all 

 respects with the white filaments of the areolar tissue already described. 

 Like these they are collected into bundles, in which they run parallel and 

 exhibit the same wavy character, cohering very intimately. The bundles 

 appear to the naked eye as fine shiaing threads or narrow flattened bands 

 for they vary greatly in thickness. They either run all in one direction as 

 in long tendons, or intersect each other in different planes as in some 

 aponeuroses, or they take various directions and decussate irregularly with 

 each other as in the dura mater. And when they run parallel to each other, 

 as in tendon, they do not keep separate throughout their length, but send 

 off slips to join neighbouring bundles and receive the like in turn ; so that 

 successive cross sections of a tendon or ligament present different figures 

 of the sectional areas of the bundles. A sheath of dense areolar tissue 

 covers the tendons and ligaments on the outside, and a variable amount of 

 the same tissue lies between the larger fasciculi ; little in tendons, more in 

 some fibrous membranes. 



The filaments swell up and become indistinct when acted on by acetic 

 acid, like those of areolar tissue, and here also the acid discloses the exis- 

 tence of corpuscles and of elastic fibres, intermixed in small proportion with 

 the rest of the tissue. The elastic fibres are fine and generally branched 

 and connected together. The corpuscles, which have no real connection 

 with the elastic fibres, are for the most part lodged where the angles of the 

 fasciculi (which are usually prismatic in form) meet. They are fusiform or 

 lanceolate in figure, pointed at the ends, and lie lengthwise among the 

 bundles. In cross sections there is an appearance of radiating pointed pro- 

 cesses, diverging from the spots where the corpuscles are situated, and these 

 have been taken for branches or offsets extending laterally from these bodies; 

 but it seems to be satisfactorily shown that the apparent branches are 

 merely the crevices between the fasciculi, diverging from the poiut where their 

 angles meet. But although these fissures do not contain branches radiating 

 from the corpuscles, flat membraneous shreds can here and there be extracted 

 from them, which are by some supposed to be part of a membrane by which 

 each several bundle is ensheathed and separated from its neighbours. 



The surface of a tendon or of any other part consisting of this texture, 

 appears marked across the direction of the fasciculi with alternate light and 

 dark streaks, which give it a peculiar aspect, not unlike that of a watered 

 ribbon. This appearance is owing to the wavy course of the filaments, for 

 when the light falls on them their bondings naturally give rise to alternate 

 lights and shadows. 



The fibrous and areolar tissues thus agreeing in their ultimate structure, 

 it is not to be wondered at that sometimes the limits between the two should 

 be but ill-defined, and that the one should pass by inconspicuous gradations 

 into the other. Instances of such a transition may be seen in many of the 

 fasciae : these at certain parts consist of dense areolar tissue, but on being 

 traced farther are seen gradually to take on the fibrous character ; and 

 fascise, which in one body consist of areolar tissue, may be decidedly fibrous 

 in another. 



In chemical constitution also the fibrous tissue is similar to the areolar. 

 It contains about two-thirds of its weight of water ; it becomes transparent, 



