OSSEOUS TISSUE. 31 



T. S. SHAFT OF A DENSE BONE DECALCIFIED. 



EXAMINATION (L). (a) Osmic acid section. Float the section on to a slide from weak 

 spirit, remove the surplus spirit, add a drop of melted glycerine jelly (p. xlviii), and cover. 

 (Glycerine and Farrant's solution render the tissues too transparent.) Observe the periosteum 

 surrounding the ring of bone. If the section be made through the centre of the shaft there will 

 be little cancellated tissue only a ring of dense bone surrounding the medullary cavity. In 

 the bone observe the Haversian canals, some divided transversely, others obliquely, and some 

 are opened into longitudinally ; arranged with reference to these are the bone-corpuscles lying in 

 their lacunae, which appear like little dark specks. Some lacunas are arranged with reference 

 to the periphery of the bone. The lamellae of bone may be faintly seen. Those arranged round 

 the Haversian canals are the Haversian lamellae, and these with the lacunae and their cana- 

 liculi and Haversian canal make up a Haversian system, the peripheric lamellae arranged 

 with reference to the periphery of the bone, and lastly some segments of larger circles which 

 lie jammed up between the Haversian systems, though not belonging to them the interme- 

 diary lamellae, which are segments of greater circles than the Haversian lamellae. This in- 

 dicates that at one time they were situated under the periosteum, but in process of develop- 

 ment they have come to lie amongst the Haversian systems. They never contain a Haversian 

 canal. (Indicate these general characters in PL VI., Fig. I.) 



(H). Observe the outer and inner layers of the periosteum and perhaps a layer of somewhat 

 flattened cells lying directly on the bone between it and the periosteum the osteoblasts. 

 Observe the bone-matrix with the faintly indicated lamellae, and the bone-corpuscles irregular, 

 somewhat shrunken, nucleated masses of protoplasm, each lying in a space or lacuna, with faint 

 indications of the canaliculi. The Haversian canals, opened into longitudinally, may be seen 

 to contain osteoblasts and a blood-vessel. (Indicate these structures in PL VI., Fig. 2.) 



(b) Stain a T. S. of the shaft with picrocarmine for ten minutes, and mount it in Farrant's 

 solution or glycerine jelly. Cover. (L). The periosteum is now well defined, its outer layer 

 being stained red, from its consisting chiefly of white fibrous tissue, whilst the deeper layer is 

 somewhat yellower in colour. The matrix of the bone is yellow and the bone-corpuscles red. 



(H). The outer layer of the periosteum is now seen to consist of bundles of fibrous tissue 

 crossing each other, mixed with a few elastic fibres ; the deeper yellow-coloured layer consists 

 of a large proportion of elastic fibres, mostly arranged longitudinally, and so their cut ends 

 appear as dots, and lying on the bone is a layer of flattened nucleated cells stained yellow the 

 osteoblasts. 



L. S. OF A DENSE BONE DECALCIFIED. 



EXAMINATION (L). Observe the Haversian canals cut into and arranged for the most part 

 longitudinally, with here and there transverse or oblique canals connecting them ; the rows of 

 lacunae five or more between two Haversian canals ; the lacunae are flattened, with their long 

 axis in the axis of the bone, and from each surface they give off canaliculi. If the periosteum 

 has been preserved the osteoblasts may be traced into a Haversian canal opening on the 

 surface of the bone. (Indicate the Haversian canals and lacuna in PL VI., Fig. 3.) 



(H). Observe the lacunae with their included bone-corpuscles ; in the Haversian canals 

 the remains of blood-vessels and osteoblasts. 



