ARTICULAR CARTILAGE. 91 



fresh condition it presented, a coarsely granular 

 appearance, so much so indeed that, the nucleus 

 which was previously so apparent is now entirely 

 obscured. Moreover, as already indicated, the car- 

 tilage-cell no longer fills the cell-space in which it 

 lies. The cells always undergo this change after 

 death, unless the tissue has been treated with some 

 reagent which prevents its occurrence. 



In preparing a specimen of cartilage with the 

 object of permanently preserving it, our aim should 

 be, as, indeed, with every tissue, to obtain it in a 

 condition and form as nearly as possible approaching 

 that which it had whilst living. There are nume- 

 rous reagents which, in place of acting like water 

 and causing contraction of the cartilage-cells, fix 

 them in the form they present during life. Amongst 

 these osmic acid may be mentioned first, as the most 

 generally valuable reagent which we possess for this 

 purpose, since it acts in like manner upon nearly all 

 the tissues. But it will not here be recommended 

 for the purpose of preserving the tissue of cartilage 

 in consequence of its costliness, and from the fact 

 that other and cheaper reagents serve the purpose 

 equally well. One special value it certainly has, 

 however ; namely, in showing that the little granules 

 in the protoplasm of the cartilage-cell are many of 

 them of a fatty nature, for they are blackened by 

 the reagent. A one per cent, solution of alum, and 

 a saturated solution of picric acid (both recom- 

 meded by Ranvier), preserve the cells of cartilage 

 admirably. But one of the best and most conve- 

 nient reagents for the purpose is a weak solution of 

 chromic acid (1 part to 600 of water). 



Preparations 2 and 3. The articular head of 

 one of the long bones is removed from the recently 

 killed animal, split into two down the middle with 

 a strong knife or a chisel, and the halves placed in 

 a large quantity of a solution of chromic acid of the 

 strength above indicated, and allowed to remain in 

 it a few days. The exact time is immaterial, but in 



