24 



PHYSIOLOGY. 



examination of all these different classifications. That one has been 

 adopted which seems to be most generally received. 



The elementary membrane was alluded to and described, as far 

 as seemed requisite, in the commencement of this article ; we proceed 

 at once, therefore, to the consideration of the second group of tissues, 

 the fibrous. 



OF THE SIMPLE FIBROUS TISSUES. 



Under this head are included two kinds of texturoj resembling 

 each other only in the fact that they present to the eye a fibrous 

 aspect. They differ in their ultimate structure, colour, and pliysic^' 

 properties. They are both used in connexion with the skeleton, and 

 are concerned in the mechanism of animal motion and locomotion. 

 They are known as the white and yelloiv fibrous tissues. 



It will be remembered that there is reason to doubt whether they 

 are generated by a metamorphosis of cells, or whether they are not 

 produced by the consolidation of a plastic fluid which has been 

 elaborated by cells ; the latter is the more probable hypothesis. 



The white fibrous tissue is found in textures requiring great flexi- 

 bility, strength, and an unyielding firmness ; such as ligaments, 

 tendons, fibrous membranes, aponeuroses, &c. It presents itself in 

 the form of inelastic bands, somewhat wavy in their direction, some- 

 times arranged side by side, at others, disposed on different planes, 

 and interlacino; and crossin<j in various 

 directions. (Fig. 3.) It is inelastic, and under 

 ordinary circumstances, inextensibh ; con- 

 tains but few vessels, and no nerves, at least 

 they have never been satisfactorily disco- 

 vered. It seems entirely destitute of any 

 vital properties ; and its chemical nature is 

 such that it needs very little interstitial 

 change to maintain its normal composition. 

 It yields gelatine in considerable quantity 

 by boiling. When treated with acetic acid 

 it immediately swells up and becomes trans- 

 parent. 



When a solution of continuity takes place 

 in this tissue it is readily repaired by the in- 

 terposition of a new substance, in every re- 

 spect resembling the original, save, that it 

 wants the peculiar glistening aspect, and is 

 more bulky. 

 Yellow fibrous tissue, differs from the last in colour, and in the 

 possession o^ great elasticity. It consists of bundles of fibres covered 



* 2. Straight appearance of the tissue when stretched. 1, 3, 4, 5. Various wavy appear- 

 ances which the tissue exhibits when not stretched. 



Fig. 3.* 



