CHAP. III.] FIBROUS TISSUE. 71 



They constitute one of the anatomical characters of an enarthrodial 

 or ball-and-socket joint, and are found in the only two perfect 

 examples of that form of articulation, namely, the shoulder and 

 hip joints. 



B. Tendons. Tendons serve to attach muscle to bone, or some 

 other part of the sclerous system. We may enumerate three 

 varieties of tendon, as regards form: 1. Funicular, e.g. long ten- 

 don of the biceps cubiti ; 2. Fascicular, short tendon of the same 

 muscle, and most of the tendons of the body ; 3. Aponeurotic, ten- 

 dinous expansions, sometimes of considerable extent, and very 

 useful in protecting the walls of cavities. The tendons of the 

 abdominal muscles afford good examples of this variety. 



The tendons are for the most part implanted by separate fascicles 

 into distinct depressions in the bones, and are also closely incor- 

 porated with the periosteum ; so that in maceration, when the 

 latter is separated, it becomes easy to remove the tendons. In 

 some birds whose tendons are black, the periosteum is black also ; 

 and in the human subject we may often see the tendinous fibres 

 continued on the surface of the periosteum, as a shining silvery 

 layer, following the primitive direction of the tendinous fibres, from 

 which they were derived ; a marked example of this may be seen 

 on the sternum, in front of which the tendinous fibres of the oppo- 

 site pectoral muscles meet and decussate, and thus form the super- 

 ficial layer of the periosteum covering that bone. The length of 

 the tendons is beautifully adapted to the quantity of contractile fibre 

 required to perform a certain movement ; thus, in the biceps cubiti, 

 were the whole length between the scapula and radius occupied by 

 muscular fibre, there would be a great waste of that contractile 

 tissue, as there would be much more than is wanted to produce the 

 required motion ; tendon is, therefore, made to take the place of 

 the superfluous muscle : in this way we may explain the differences 

 in length of the tendons even in the same limb. 



C. Membranous. In the form of an expanded membrane white 

 fibrous tissue is used to cover, protect, and support various parts. 

 Under such circumstances we often find that it not only forms an 

 external covering to them, but that it sends in processes or septa, 

 which separate certain subdivisions or smaller parts. Thus, the 

 fascia lata of the thigh not only invests the muscles of the thigh, 

 but sends in processes which pass down to the periosteum, and 

 separate the several muscles from each other ; and the dura mater 

 of the cranium sends in processes by which certain portions of the 

 encephalon are separated from one another. 



