ON THE STRUCTURE OP HYALINE CARTILAGE. 3 



The cartilage covering the head of a frog's femur, or that 

 of a small niammal, is -well adapted for treatment by the 

 potash solution. The author has generally cut off the head 

 of the bone and placed it in the solution at the temperature 

 indicated. In a few minutes it falls to the bottom of the 

 vessel, and it can then be removed to a glass slip for 

 examination. 



The outer pellicle which represents the cartilage can be 

 easily separated by needles and examined. The substance pro- 

 per (matrix) of the cartilage can be always seen, but variously 

 modified in different preparations, and some appearances 

 having relation to its arrangements and structure which 

 have not hitherto attracted much attention can frequently 

 be observed ; but as these can be better studied by methods 

 shortly to be indicated, it is not necessary to describe them 

 here. 



A successful potash preparation shows flattened polygonal 

 cells adhering to each other exactly like an epithelium. In 

 contour, mutual arrangement, and appearance generally they 

 are absolutely indistinguishable from any ordinary epithelial 

 layer. No histologist who had once observed them could 

 hesitate to classify them as a variety of epithelium, especially 

 when the mode of preparation is taken into account. They 

 are seen differently according to the degree in which the 

 j)otash has acted on the ground-substance. Sheets of cells and 

 more rarely isolated cells are sometimes seen floating free in 

 the liquid. At other times the cells may be seen lying on 

 the surface of considerable fragments of the ground- substance. 

 These fragments sometimes shoAv depressions corresponding 

 in outline, diameter, and relative position with what have been 

 usually described as the cavities or capsules in Avhich the or- 

 dinary cartilage-cells are situated, and when the flat cells on 

 them are visible it can be seen that the so-called capsules 

 consist of depressions in the ground-substance, and that the 

 depressions and the more even surface in which these are 

 situated are covered with a continuous epithelial layer. 

 Such a preparation at once shows that the idea of a closed 

 cavity in the ground-substance harbouring a cell has been 

 founded on imperfect methods of observation. Between the 

 free sheets of cells and those seen adhering to the ground 

 substance and its depressions there is an appearance some- 

 times seen which is intermediate as regards the solvent effect 

 of the solution. The potash may preserve entire a substance 

 which may be described as an interepithelial framework. It 

 follows the lines and angles between the cells, and can be 

 distinouished as differins both from the cells and the ground- 



