118 [December, 



their surface, the biokenedge presenting a striated appearance in the same direc- 

 tion. This character the older anatomists ascribed to a fibrous or columnar 

 structure of the cartilage, like that of the enamel of the teeth, -while histologists 

 at the present day, consider it as dependent upon the vertical arrangement of the 

 rows of cartilage cells, although it has been suspected to depend upon some 

 ultimate arrangement of the matrix or intercellular substance not yet detected. 

 In some late observations upon the structure and development of articular carti- 

 lage, through means of an excellent microscope, made for me by Messrs. Powell 

 & Lcaland, of London, I have been enabled to discover a definite structure in 

 the intercellular substance. This consists of an arrangement of exceedingly 

 fine, transparent filaments, nearly uniform in thickness, and having an avera2<^ 



measurement of the -t- of an inch. An easy method of detecting this fila- 



2 5 •' ^ '^ 



mentous structure, is to tear a fine fibre from the broken edge of an articular 

 cartilage which has been macerated in diluted muriatic acid, by means of a 

 fine pointed forceps, and exposing it in the ordinary way in water beneath 

 the microscope, using the quarter or eighth inch objective power. The 

 fine filaments, partly detached, will be seen in great numbers along the 

 sides of the fibre. When these filaments are viewed by very oblique light, 

 they appear to have an indistinct granular appearance, each composed of a single 

 row of granules, which of course, in the articular cartilage, adhere together with 

 greater tenacity in the direction of the length of the filaments than laterally. 



When an articular cartilage is broken in a direction from the under to the free 

 surface, it is found that the fragments adhere by a membranous layer, cover- 

 ing the free surface of the cartilage, which, by the older anatomists, was 

 considered as the extension of the synovial membrane; by the anatomists of 

 our day, either as a homogenous layer, or as nothing more than a stratum of the 

 cartilage the rows of cells of which take a direction parallel with the surface, 

 or at right angles to those more deeply situated, and thus giving ri?e to this dis- 

 tinct laminated condition. That it is a cartilaginous layer is undoubtedly correct, 

 but instead of the rows of cells determining the arrangement, I find it depends 

 upon the filamentary structure of the matri.x, the filaments taking a course 

 parallel with the surface of the cartilage, in a direction at right angles to those 

 forming the matrix of the deeper part of the cartilage. 



A straight fibre may be torn from the articular cartilage, and in the act of 

 tearing, should a row of cells be in the line of rupture, as is frequently the case, 

 (for although generally following the course of the filaments, yet a number are 

 oblique or even somewhat irregular,) it will be torn through, which in itself 

 would be suflicient to indicate that the fibrous arrangement of the cartilage did not 

 depend upon its rows of cells, and indeed they have but little or no influence in 

 this respect. 



From the foregoing description of the structure of the intercellular sub- 

 stance of articular cartilage, it can be readily understood that it may deter- 

 mine the course of the rows of cells, which is really the case. In the earliest 

 period of the existence of the articular cartilage, the cartilage cells are 

 single, isolated, and equally diffused throughout a mass of hyaline substance, 

 which latter in the progress of development becomes indistinctly granular, 

 and then for the first time have I observed the appearance of the filamen- 

 tary structure. In the splitting up of the primary cartilage cell and deve- 

 lopment of others, they arrange themselves in the direction in which there is 

 least resistance, which would be of course in the direction of the filaments of the 



