CELLULAR OR FIBROUS TISSUE. 333 



when one bends a bundle strongly. But in many situa- 

 tions they are interlaced, and held together by filaments, 

 which differ from the fibres of cellular tissue by their 

 chemical and microscopical peculiarities, while in certain re- 

 spects they approach the fibres of elastic tissue ; of which 

 we shall give a description further on. They are almost 

 still finer than the fibres of cellular tissue, quite flat and 

 homogeneous, but with outlines much more obscure, and 

 they are distinguished, above all, by the considerable folds, 

 which they describe when they are in a state of separation. 

 In order to recognise them, it is necessary to place the cellular 

 tissue in contact with acetic acid : in this acid the bundles 

 of cellular tissue become transparent, swell, and cease to 

 appear fibrous, while the filaments which envelope them 

 undergo no change. In this manner it happens that a 

 bundle, which appears to be composed of the ordinary 

 interlaced fibres of cellular tissue, comports itself after 

 having been treated with acetic acid, as a transparent 

 cylinder divided by contractions often very regular, and 

 which one soon observes to be caused by a filament which 

 runs spirally around the bundle ; or also by separated rings 

 placed at a greater or less distance from each other. I have 

 rarely succeeded unreducing the turns to a single filament, 

 and I am obliged in consequence to leave undecided the 

 question, whether it does not sometimes happen that many 

 filaments are rolled spirally around a bundle. The forma- 

 tions which I have described show themselves in no part in 

 a more beautiful manner than in the delicate and firm 

 cellular tissue, which is situated at the base of the brain 

 beneath the arachnoid, between the vascular trunks and the 

 nerves, and which becomes distended into isolated filaments, 

 on extension, as for example, in any part of the circle of Willis. 

 There I have never sought the spiral filaments in vain ; 

 nevertheless analogous bundles, encircled with spirals, may 

 be seen also upon other parts of the economy, in serous 

 membranes, in the subcutaneous cellular tissue, in the skin, 

 and even in the tendons." * 



* Anat. Gen. vol. i. pp. 377, 378. 



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