CHAP. IV.] CARTILAGE. 93 



used, it would apply equally to all tissues, except the lining mem- 

 brane of the vascular system itself, which is probably nourished by 

 the blood immediately in contact with it. 



Returning from this digression, we remark, that temporary car- 

 tilage, when in small mass, is not permeated by vessels ; but that, 

 when more than about an eighth of an inch thick, it contains canals 

 in its interior, for the transmission of vessels. These canals are 

 somewhat tortuous, and contain a delicate extension of the peri- 

 chondrium. They may be regarded as so many involutions of the 

 outer surface of the cartilage. 



The same description will apply to the various membraniform 

 cartilages, with this difference, that their blood-vessels are less 

 numerous. In those which are thin, no vascular canals are to be 

 found ; but where there is much substance, as in the costal carti- 

 lages, they are easily detected. 



Nothing is more certain than that articular cartilage, in man, is 

 not penetrated by blood-vessels. Coloured fluids injected into the 

 vessels cannot be made to enter it, but are seen to turn back, on 

 reaching it, into the tissue which conveyed them to it. But we 

 possess a more certain test than this, in the examination of thin 

 slices of the tissue under a high power. This brings no vessels into 

 view : on the contrary, it proves their non-existence beyond dis- 

 pute. In some diseased states, however, the presence of a few 

 vessels seems to have been established. 



Mr. Toynbee* has pointed out, that the vessels of bone, at the 

 part on which cartilage rests, are separated from the cartilage by a 

 bony lamella, in which no apertures exist. The minute vessels, on 

 approaching this lamella seem to dilate, and then, forming arches, 

 they run back into the cancelli of the bone. Such an arrange- 

 ment must, of course, be attended with a retardation of the blood 

 near the " articular lamella." The vessels of the synovial membrane 

 advance with it a little way upon the articular surface of the car- 

 tilage, but only over those parts which are not subject to pressure 

 during the natural movements of the joint. These likewise ter- 

 minate in loops. In diseased states they often advance far upon 

 the cartilage as they do naturally, according to Mr. Toynbee's 

 observations, during the middle period of foetal life. 



* Phil. Trans. 1841. 



