OF NON-VASCULAR ANIMAL TISSUES. 169 



These vessels form a band which surrounds the circumference of the articular car- 

 tilage in all joints, as has been above stated. 



In the foetus, the vessels forming the band are long, while in the young and adult 

 subject they are shorter, having receded to the margin of the cartilage which is not 

 subject to concussion. 



In the foetal subject this band is more broad in some parts than others ; but 

 those portions of it which project to an inconsiderable extent over the surface of the 

 cartilage, have, on the opposite part of the circumference, others which project to a 

 considerable extent. 



f^arious Characters of the Synovial Vessels. — ^These synovial vessels consist of arte- 

 ries which take a direction towards the centre of the articular cartilage, and of veins 

 which take a retrograde course. The arteries become continuous with the veins in 

 the following ways : — 1st, the artery becomes directly continuous with the vein without 

 undergoing any change in its size, forming with the latter a simple loop (Plate XIII. 

 fig. 1.) ; 2ndly, numerous arteries terminate in a single vessel from which veins arise; 

 (this disposition is evident in the knee-joint, Plate XIV. fig. 2. and Plate XIII. fig. 5.) ; 

 3rdly, the artery terminates in largely dilated vessels, from which the veins take 

 their origin, Plate XIII. figs. 3 and 4. 



The preceding account of the examination of the vessels of articulations at early 

 periods, shows that a large quantity of blood-vessels exists both at the free and 

 attached surface of articular cartilage during its development. The modes in which 

 these vessels are disposed, the dilated, plexiform, and other characters which they 

 present at the point of communication of the arterial with the venous system, are 

 interesting features in the anatomy of the vascular system, and their presence here 

 must be associated with the large quantity of fluid required for the nutrition of the 

 articular cartilage during development, and which is eliminated from the blood 

 whilst its course is retarded in these vessels*. 



C. Adult Articular Cartilage. 



I have now to speak of the nutrition of articular cartilage when perfectly developed, 

 and subject, in the performance of its functions, to violent concussion, compression, 

 &c. 



In reference to the structure of adult articular cartilage, it has already been stated 

 that at its attached surface, viz. at the part where it joins the osseous lamella, it pre- \ 

 sents numerous fine canals, which can be seen only with the higher magnifying powers. 

 These canals are irregular in their distribution ; some are merely dilated cavities ; 

 frequently several of these cavities are elongated, and arranged serially, running from 

 the attached towards the free surface of the cartilage. At the free or synovial sur- 

 face, these canals do not exist ; the cells of the texture at this part being elongated 



* I have frequently found the sac of the synovial membrane full of colourless size, in joints of which the 

 vessels have been successfully filled with an injection composed of size and vermilion. 



