Ixxii 



AREOLAR TISSUE. 



In certain portions of the areolar tissue, as for instance in that which lies 

 under the serous and mucous membranes of particular regions, the yellow or 

 elastic fibres are abundant and large, so that they cannot well be overlooked ; 

 but in other parts they are few in number, and small, and are then in a 



great measure hidden by 



Fig. XXXVI. the white filaments ; in 



such cases, however, they 

 can always be rendered con- 

 spicuous under the micro- 

 scope by means of acetic 

 acid, which causes the white 

 filaments to swell up and 

 become indistinct, whilst 

 the elastic fibres, not being 

 affected by that re- agent, 

 come then more clearly into 

 view (fig. xxxvi.). Under 

 the microscope the elastic 

 fibres appeartransparentand 

 colourless, \\ith a strong, 

 well-defined, dark outline. 

 They are, moreover, remark- 

 able for their tendency to 

 curl up, especially at their 

 broken ends, which gives 

 them a very peculiar aspect ; 

 and in many parts of the 

 areolar tissue they divide 

 into branches and join or 



anastomose with one another, in the same n.anner, as in the pure elastic 

 tissue (a). They differ among themselves very widely in size, some being 

 as fine as the white filaments, others many times larger. 



In the immature areolar tissue of the foetus there is a considerable amount 

 of soft jelly-like matter, of muco-albuminons nature, in the interstices of 

 the formed elements. This amorphous substance is for the most part incon- 

 spicuous in the perfected tissue, but exists abundantly in the umbilical cord, 

 where it forms the well-known Whartonian jelly ; it may also be seen, at all 

 periods, but in smaller quantity, in the areolar tissue within the vertebral 

 canal. 



A very different view of the structure of areolar tissue from that here 

 stated was taken by Reichert, and adopted by Virchow, Donders, and other 

 distinguished histologists. According to tbis view the apparent bundles 

 consist of a substance in reality amorphous or homogeneous, aud its seeming 

 fibrillation is partly artificial, the result of cleavage, and partly an optical 

 illusion, arising from creasing or folding. In point of fact, however, the 

 bundles readily separate into fibrils after exposure to dilute solutions of 

 chromic acid, or to lime-water, or to baryta- water, by which the uniting 

 matter is dissolved ; so that there can be no doubt of their truly fibrillar 

 structure. At the same time it is not denied that immature fasciculi may 

 probably occur, in which the fibrillation is incomplete. Moreover, a homo- 

 geneous substance, not to be confounded with the soft jelly-like matter 

 previously noticed, but of firm consistence and agreeing in chemical nature 

 with the fibrils, envelopes the fasciculi in some situations in form of a fine 



Fig. XXXVI. MAGNIFIED VIEW OP AREOLAR TISSUE 

 (FROM DIFFERENT PARTS) TREATED WITH ACETIC 

 ACID. 

 The white filaments are no longer seen, and the 



yellow or elastic fibres with the nuclei come into view. 



At c, elastic fibres wind round a bundle of white fibres, 



which by the effect of the acid is swollen out between 



the turns. 



