394 THE ANAT02k[Y OF THE HORSE 



ligamentum colli, the cliordise vocales, and membranes of the larnyx and 

 trachea, and the middle coat of the arteries. 



Red fibrous tissue, also called contractile tissue from its possessing the 

 power of contracting under certain stimulants, is intermediate between 

 3-ellow fibrous tissue and muscular fibre. Its fibres are cylindrical, trans- 

 parent, of a reddish colour, and collected in bundles. It has no connection 

 with the joints, but is met with in the iris, around certain excretory ducts, 

 and in the coats of the veins. 



Chemical Comjjosition.^ — The flexibility of fibrous tissue is owing to 

 the presence of water in it, of which it contains about two-thirds of its 

 weight. A tendon or ligament will readily dry and become brittle. 

 Acetic acid causes it to swell up, and here the acid discloses the existence 

 of nuclei and elastic fibres. It is chiefly composed of gelatine, which is 

 extracted by boiling. 



Blood-vessels. — White fibrous tissue contains few blood-vessels. They 

 usually follow the course of the fasciculi ; in ligaments they run in a 

 longitudinal direction, sending off communicating branches across the 

 fasciculi, and eventually forming an open network. The periosteum is much 

 more vascular, but the vessels do not strictly belong to the membrane, as 

 the ramifications found in it are chiefly intended for supplying blood to the 

 Ijone which it covers. 



Nerves. — Small tendons contain no nerves, and large ones only small 

 filaments. In the periosteum, nerves are abundant ; they exist there 

 chiefly for supplying the bones with sensibility. The pain caused in rheu- 

 matism, which is an intensely painful disease, is a proof of the sensibility of 

 white fibrous tissue. 



FIBRO-CARTILAGE 



This substance, intermediate in structure and uses between cartilage 

 and fibrous tissue, is composed of a network of white glistening fibres col- 

 lected into fasciculi of various sizes, and containing within its meshes cells 

 and a sub-fibrous tissue resembling that of true cartilage. Fibro-cartilage 

 admits of arrangement in four groups : — 



1. Interarticular fibro-cartilage is placed between the moving 

 surfaces of bones. It serves to connect them together, to facilitate their 

 gliding motion, and to act as a cushion, thus preserving the articular sur- 

 faces from attrition, and the bones from the efiects of sudden concussion. 

 It is usually placed where much motion is enjoyed, as in the lower jaw 

 and knee, in the form of round oval plates growing thinner in the centre. 

 Marginal cartilages such as that around the cotyloid cavity are of the same 

 kind. 



2. Stratiform fibro cartilages form a thin coating to the bony grooves 

 over which tendons play. 



3. Interosseous fibro-cartilage occurs between the vertebra?, at the 

 ischio-pubic symphysis, etc. 



4. Free fibro-cartilages are met with in the tarsal cartilages of the 



eyelids, etc. 



