CARTILAGE. 15 



amongst the best of these is a saturated watery solution of picric acid. Take costal and 

 articular cartilage as types. 



Place small pieces not larger than half an inch of the costal cartilages, with their peri- 

 chondrium, of a cat or rabbit or human fcetus, in a saturated watery solution of picric acid for 

 forty-eight hours. Then remove them and wash them thoroughly in water till no yellow 

 colour is given off, and place them in rectified spirit till they are required. Sections may be 

 made either with the hand or by means of a freezing microtome (p. xxxviii). It is well to 

 practise making sections with a razor, and cartilage, from its consistence, is one of the easiest 

 tissues to begin with. A similar procedure is adopted for adult Intman costal cartilage, and also 

 for articular cartilage. If the costal cartilage contain any bony or calcareous matter, macerate 

 it for one or two weeks in the acid till all the calcareous matter is removed. For articular car- 

 tilage, if it be desired to have a section of the subjacent bone, the bone must be softened by 

 means of an acid which removes the calcareous matter. It may be accomplished thus : Place 

 the articular end of, say, the femur or humerus of a recently killed cat or rabbit in a large 

 quantity (twenty to thirty times the bulk of the tissue) of one of the following solutions : 



(a) A saturated watery solution of Picric Acid. Change the fluid at the end of a week and 

 add fresh solution containing a few crystals of picric acid. The bone will be softened in from 

 two to three weeks. 



(U) A quarter per cent, solution of Chromic Acid may be employed. Take care to change the 

 fluid after three days. This fluid requires also from two to three weeks to decalcify the bone. 



(c) A mixture of Chromic Acid and Nitric Acid (p. xxxiii) may be employed. Similar con- 

 ditions obtain as in (a) and (3). 



(</) Or a two per cent, solution of Hydrochloric Acid may be used as the decalcifying agent. 



(a) and (c) are the methods which yield the best results. 



COSTAL CARTILAGE. 



Make a number of transverse sections of the costal cartilage of a kitten or young rabbit, and 

 also of the decalcified costal cartilages of an old person, prepared as described above. These 

 sections may be examined as they are or after being stained. 



A. FROM A YOUNG ANIMAL. 



(a) Osmic Acid. Place some of the sections of the kitten's cartilage in a one per cent, solu- 

 tion of osmic acid for twelve hours. Wash them thoroughly in water, to remove the osmic 

 acid. Mount one in Farrant's solution, and cover. These sections are taken, first, because 

 they are small and one sees better the general characters of the section 



EXAMINATION (L). Observe the fibrous perichondrium and the cartilage-matrix inside 

 it, the cartilage-corpuscles, small and flattened, lying in several layers. Nearer the centre of 

 the section are seen, as small specks, the irregularly shaped corpuscles. The corpuscles are 

 stained of a deeper yellow than the matrix by the osmic acid, hence its value. (H) Examine 

 the fibrous perichondrium with its areolar tissue and sections of elastic fibres. Observe the 

 cartilage-cells flattened towards the periphery of the cartilage, and the more rounded charac- 

 ter of the cells placed nearer the centre. Otherwise the cells and matrix have the same 

 characters as are indicated in fresh hyaline cartilage. 



() Carmine. Stain a section with carmine. Lay a section on a slide and on it place a 



