34 PRACTICAL HISTOLOGY. 



and into the medullary cavity. The lacunae are long, narrow ovals, parallel to the canals 

 arranged in several rows between adjoining canals. 



BLOOD-VESSELS OF BONE. 



PREPARATION. Place the leg-bones of a rabbit whose blood-vessels have been injected 

 with a gelatine and carmine mass (p. li), in a three per cent, solution of hydrochloric acid 

 for several days, until they are completely decalcified. Place them in water for several hours, 

 and afterwards in a dilute solution of sodic carbonate, to get rid of the last. trace of acid. 

 Make longitudinal and transverse sections in the ordinary way, and mount them in Farrant's 

 solution. 



EXAMINATION (L). Observe each Haversian canal contains a blood-vessel, and note the 

 general arrangement, which follows exactly the Haversian canals. {Indicate the longitudinal 

 arrangement of tlie blood-vessels in PL VI., Fig. 3.) 



CANCELLOUS DECALCIFIED BONE. 



PREPARATION. Soften the head of a fcetal bone of a kitten or new-born child in the 

 usual way, and make transverse sections through the cancellous head of the bone. Stain a 

 section with logwood for five minutes, and another with picrocarmine for fifteen minutes, and 

 mount both in Farrant's solution. Cover. 



EXAMINATION (L). Observe the open meshwork ; the meshes are the cancelli, bounded 

 by trabeculse of bone, which do not contain Haversian canals. In the cancelli are osteoblasts 

 and marrow-cells. 



(H). Study the osteoblasts, and search for multi-nucleated cells (myoplaques, giant-cells, or 

 osteoclasts) cells several times larger than the osteoblasts, containing many nuclei imbedded 

 in granular protoplasm. They usually lie close on the bone, in a depression which they 

 accurately fill. 



DEVELOPMENT OF BONE (INTRA-CARTILAGINOUS). 



PREPARATION. Place the leg-bones of a rabbit, one week old, or those of a kitten, in 

 picric acid solution, or in the chromic acid and nitric acid fluid, till they are completely softened. 

 Make a longitudinal vertical section through the cartilaginous head and shaft of the bone. 



EXAMINATION (L). Stain a section with picrocarmine. Observe the head of the bone 

 separated from the shaft by the epiphysial cartilage, and below the cartilage the line of ossifi- 

 cation. In the epiphysial cartilage the cells are arranged to a certain depth above the line of 

 ossification in rows parallel to the long axis of the bone. These rows of cells are produced 

 by transverse cleavage of cartilage-cells. Below the line of ossification, where true bone com- 

 mences, are found irregular spaces the primary medullary spaces which are bounded by 

 narrow spicules of calcified cartilage, partially covered by a layer of bone. In these spaces 

 are seen osteoblasts, young marrow-cells, and blood-vessels. 



(H). Observe the rows of cartilage-cells, smaller above and larger below. At the line of 

 ossification a cartilage-capsule may be found, opening and discharging its contents into a 

 primary medullary space. The long spicules have in their centre the remains of the calcified 

 cartilage, and on them is deposited bone, which is now stained of a deep red colour, and 

 osteoblasts may be seen in process of becoming imbedded in this newly formed bone, to form 

 bone-corpuscles. In the spaces observe the osteoblasts, and here and there multi-nucleated 



