ON' THE STUUCTUUE OV IIYALIKE CARTILAGE. 11 



In a paper presented to the Royal Society, an abstract of 

 which is published in the 'Proceedings/ No. 158, 1875, the 

 author has described a number of appearances seen by the 

 application of a method which he thus summarised : — " Trans- 

 parent animal tissues, when sealed up fresh in aqueous 

 humour or blood-serum by running BrunsAvick black round 

 the edge of the cover-glass, undergo a series of slow changes, 

 by which, generally within a period of two to five days, 

 anatomical elements, mostly otherwise invisible, become 

 distinct." It was in studying cartilage in the sclerotic of the 

 frog that in the spring of 1874 the author observed for the 

 first time that by this method flat cells could be seen in layers 

 in cartilage. The successful preparations sealed up as de- 

 scribed in aqueous humour, andallowed to remain for 24 — 48 

 hours (at the temperature of London in June), showed, in 

 addition to a large polygonal epithelium, rows of narrow cells 

 joined to each other end to end, and in contact with other 

 rows on each side. These cells are represented in Fig. 17. 



The cells were perfectly hyaline in appearance, with the 

 nucleus well marked. Attempts made this year to obtain 

 similar preparations in the sclerotic of the frog have failed. 

 A series of observations made on sections of the articular 

 cartilage of the carpus of the sheep treated in this way 

 gave the following results. Very thin transverse sections 

 embracing the free surface of the cartilage, show after macera- 

 tion a distinct layer of rounded cells with a central nucleus. 

 Smaller layers of similar cells may be sometimes seen in very 

 thin transverse sections which do not include the surface of 

 the cartilage, but this appearance is rarely found. In both 

 cases the cells are distinguishable only by the very fine 

 borders which indicate the cell and nucleus, their refractive 

 power difiering so little from that of the surrounding medium 

 that it is only when the section is very thin, and with good 

 light and a good lens, that they need be sought for. There 

 is no granular protoplasm in the cell. The ordinary carti- 

 lage-cells, much fewer in number and more or less widely 

 separated from each other, can be always observed in such 

 preparations ; and as they are in these circumstances seen as 

 well-marked, granular, irregular protoplasmic bodies in the 

 centre of the cellular spaces, it is not possible to confound the 

 two kinds of cells. 



The narrow elongated cells seen in the sclerotic and 

 found in the cartilage of the frog's femur, by solution of 

 potash, were not seen in these preparations. 



In many of the sheep-cartilage preparations isolated fiat 

 cells were found free in the fluid. These were found when 



