Miscellaneous. 157 



Messrs. Powell and Lealand of London, I have been enabled to dis- 

 cover a definite structure in the intercellular substance. This con- 

 sists of an arrangement of exceedingly fine, transparent filaments, 

 nearly uniform in thickness, and having an average measurement of 

 the 2ToU(J tn °f an i ncn « An easy method of detecting this filamentous 

 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, covering 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 homo- 

 geneous 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 rise to 

 this distinct 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 

 matrix, 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 irregu- 

 lar,) it will be torn through, which in itself would be sufficient 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 

 substance of articular cartilage, it can be readily understood that it 

 may determine 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 through- 

 out 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 filamentary structure. 

 In the splitting up of the primary cartilage- cell and development 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 intercellular matrix. Hence, in the deeper part of the articular 

 cartilage, the rows of cells are generally vertical to the surface, and 

 parallel to the same in its more superficial portion. 



