224 OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



1. Of ike Simple Fibrous Tissues. 



219. The various components of the Vegetable fabric its cells, tubes, woody 

 fibres (or elongated cells), &c., being destined to retain their relative situations 

 throughout their entire existence, are held together by simple adhesion; a gummy 

 intercellular substance, which answers the purpose of a cement, being often in- 

 terposed, sometimes in considerable quantity. But in the Animal body, of 

 which the several parts are designed to move with greater or less freedom upon 

 one another, the aggregations of cells that make up its chief part, either in 

 their original or in their metamorphic form, could not be held together in their 

 constantly-varying relative positions, without some intervening substance of an 

 altogether different character. It must be capable of resisting tension with con- 

 siderable firmness and elasticity; it must admit free movement of the several 

 parts upon one another; and it must still hold them sufficiently close together, 

 to resist any injurious strain upon the delicate vessels, nerves, &c., which pass 

 from one to another, as well as to prevent any permanent displacement. Now 

 all these offices are performed in a remarkably complete degree, by the Areolar 

 Tissue ( 222); the reason of whose restriction to the Animal kingdom is thus 

 evident. And as necessity arises, in certain parts, for tissues which shall exer- 

 cise a still greater power of resistance to tension, and which shall thus commu- 

 nicate motion (as in the case of Tendons), or shall bind together organs that 

 require to be united (as in the case of Ligaments and Fibrous Membranes), so 

 do we find peculiar tissues developed, that serve these purposes in the most 

 effectual manner. Hence these tissues, also, although not endowed with any 

 properties that are peculiarly animal, are nevertheless restricted to the Animal 

 Kingdom as completely as are the Muscular and Nervous Tissues, which make 

 up the essential parts of the apparatus of Animal Life. 



220. These two qualities that of resistance to tension without any yielding 

 and that of resistance combined with elasticity are characteristic of two dis- 

 tinct forms of Fibrous tissue; and these are distin- 

 guished by the hue which they ordinarily present, 

 as the White and the Yellow. The White presents 

 itself in the form of inelastic bands of variable 

 size, the largest l-500th of an inch in breadth, 

 somewhat wavy in their direction, and marked 

 longitudinally by numerous streaks (Fig. 18); 

 these streaks are rather the indications of a longitu- 

 dinal creasing, than a true separation into compo- 

 nent fibres ; for it is impossible by any art to tear 

 up the band into filaments of a determinate size, 

 although it manifests a decided tendency to tear 

 lengthwise. Sometimes, however, distinct fibres 



ma y ke Braced, whose diameter varies from about 



Ligamen . l-15,000th to l-20,000th of an inch. This 

 Magnified 65 diameters. tissue is entirely resolved into Gelatin ( 33) by 



sufficiently prolonged boiling. When treated 

 with Acetic acid under the microscope, it swells up and becomes transparent ; 

 and certain oval corpuscles are then brought into view, which seem to be either 

 the nuclei of the cells that were concerned in the formation of this tissue, or 

 the free nuclei of the blastema by whose fibrillation it was produced ( 223, 

 224). This tissue is nearly the sole component of Tendons, Ligaments, Fibrous 

 Membranes, Aponeuroses, &c., all of which present the arrangement already 

 described, with very little modification, save that the bands are often but slightly 

 wavy, and are sometimes even quite straight. If the traction to be resisted 



