HYALINE CARTILAGE. 75 



mistaken. (See fig. 44.) Near the margin of these cartilages a layer 

 of fine filamentous tissue is prolonged a certain way over their surface 

 from the synovial membrane, and the cartilage-cells in the neighbour- 

 hood of this acquire processes and present transitions to the connective- 

 tissue corpuscles of that membrane (fig. 45.) The matrix of articular 

 cartilage rarely, or perhaps never, becomes pervaded by fibres like 

 those so often seen in rib cartilage, nor is it prone to ossify. 



In the costal cartilages, the corpuscles or cells, which are of large 

 size are also collected in groups. Near the exterior of the cartilage 

 they are flattened, and lie parallel with the surface, forming a superficial 

 stratum from -o-ooth to -s^xi^h. of an inch thick. As to those situated more 

 inwardly, we can sometimes observe, in a transverse slice, that they 

 form oblong groups disposed in lines radiating to the circumference ; 

 but this arrangement is not constant, and they often appear quite irre- 

 gular. The cells, with the exception of those lying upon the surface, 

 commonly contain larger or smaller drops of oil ; and the nucleus, 

 being generally undiscoverable, is concealed by the fat or may itself 

 have undergone a fatty metamorphosis. The matrix is tolerably clear, 

 except where fibres have been developed in it, in which parts it is 

 opaque and yellowish. Such fibrous patches are very frequent ; the 

 fibres are fine, straight, and parallel, appearing transparent when few 

 together; they appear to withstand the action of acetic acid. It is not 

 uncommon to find the rib-cartilages extensively ossified. 



The description given of the microscopic characters of the costal 

 cartilages- will apply with little variation to the ensiform cartilage of 

 the sternmn, to the cartilages of the larynx and windpipe, except the 

 epiglottis and cornicula laryngis, and to the cartilages of the nose. 

 With the exception of the last, these resemble the rib-cartilages also in 

 their tendency to ossify. 



The characters of the temporary cartilages, which are hyaline, will bo 

 noticed in the account of the formation of bone. 



Vessels and nerves. — In the healthy state, no blood-vessels pene- 

 trate the articular cartilages. Whatever nutrient fluid they require 

 seems to be derived from the vessels of adjoining textures, especially 

 the bone, and to be conveyed through the tissue by imbibition. To- 

 wards the circumference of the cartilage, however, underneath the 

 synovial membrane, the synovial vessels form a narrow vascular border 

 round it, which has been named the circulus articuli vasculosus. 



When the tissue exists in thicker masses, as in the cartilages of the 

 ribs, canals are here and there excavated in its substance, along which 

 vessels are conducted to supply nourishment to the parts too distant to 

 receive it from the vessels of the perichondrium. But these canals are 

 few and wide apart, and the vessels do not pass beyond them to ramify 

 in the intermediate mass, which is accordingly quite extravascular. It 

 must be further remembered respecting these vascular canals, that many 

 of them lead to spots where the cartilage is undergoing ossification, and 

 convey vessels to supply the bony deposits. 



No nerves have been traced into any of the cartilages, and they are 

 known to be destitute of sensibility. 



Composition. — Ordinary permanent hyaline cartilage contains about three 

 fifths of its weight of water, and becomes transparent by drying. By boiling it 

 in water for iifteen or twenty hours, it is resolved into chondrin. This is a sub- 

 stance said to gelatinise on cooling, although it may be doubted whether the 



