OF NON-VASCULAR ANIMAL TISSUES. 171 



In adult life, when the epiphysal cartilage has been ossified, the cancelli of the 

 latter are separated from the articular cartilage by a layer of bone, to which may be 

 given the name of the articular lamella. The nature of this lamella is worthy of 

 particular attention. It is composed of two sets of osseous layers ; the one, dense 

 and thick, is continuous with the vertical fibres of the cancelli ; the other, delicate 

 and thin, principally composed of osseous corpuscles, is situated at right angles 

 to the latter, and fills up the interspaces of the vertical fibres*. See Plate XV. 

 figs. 2 and 3. 



It will be seen that the structure here delineated is admirably calculated to receive 

 shocks, and sustain great forces. The drawing was taken from the inferior extremity 

 of the OS femoris, to which the articular extremities of all bones more or less intimately 

 correspond. 



Is this articular lamella complete? I have never been able, by the aid of the 

 microscope, to discover any orifices in it, nor have I been able to force mercury 

 through it. 



If the articular surface of a bone, which has been minutely injected, be permitted 

 to dry, the adipose substance, a quantity of which is generally found in the interior 

 of the cancelli, in some measure permeates the osseous articular lamella, rendering 

 it transparent, and their contents may then be seen and examined. To facilitate 

 this examination, I have in some instances resorted to the application of varnish, 

 and in others have removed the earthy particles from the bone by the aid of acid. 

 Through the articular lamella numerous vessels of considerable size will be distinctly 

 recognized in the interior of the cancelli. These vessels enter the substance of the 

 bone by the large foramina which are seen at its non-articular surfaces, and they 

 converge towards the articular lamella. With the inner surface of this lamella, they I 

 not unfrequently appear to be in contact ; and either in contact with it, or near to it,/ 

 these vessels form dilatations and convolutions, and then take a retrograde course/ 

 and become continuous with the venous system. The vessels here described are reJ 

 presented as they exist towards the articular lamella in the cuneiform and cuboidj 

 bones of the adult human subject, Plate XV. figs. 4 and 5. ^ 



It is worthy of remark, that the vessels which are contiguous to the articular 

 lamella are of a considerable size. 



The existence of minute orifices in the articular lamella must be acceded to by 

 those writers, who entertain the opinion, that vessels pass from the cancelli into the 

 cartilage. I have been unable, as I have above stated, to detect the presence of these 

 minute orifices, nor have I been able to see near this lamella, the minute vessels 

 which are supposed to pass through them. 



I believe that the large vessels which I have already described as forming convo- 

 lutions and dilatations at the inner surface of the articular lamella, have the function 



* The cribriform appearance of this lamella, seen in cases of extensive disease of the articular cartilage, is 

 produced by the absorption of the thin and the persistence of the dense layer. 

 MDCCCXLI. 2 A 



