t;8 



PRACTICAL HISTOLOGY. 



[XIII. 



the lamellae, but the latter are not so distinct as in dry bone. 

 Several lamellse lie between two consecutive rows of bone-corpuscles. 

 The Haversian canab contain blood-vessels, connective tissue, and 

 other cells, or osteoblasts. 



(6.) (H) The periosteum consists of an external layer stained 

 red, and composed chiefly of white fibrous tissue. Attached to it 

 may be found small fragments of striped muscle. The internal 

 layer contains many elastic fibres, and, especially in young bones, 

 there may be seen one layer or more of flattened or cubical cells, 



Periosteum. 

 Peripherie lamellse. 

 Huversiau 

 canals. 



Haversian 

 lamella). 



Interstitial lamellae. 



Perimedullary 

 lamellae. 



Marrow. 



FIG. 149. T.S. Part of a Human Metacarpal Bone, x 50. 

 marrow. Dilute nitric acid. 



. Haversian space with 



called osteoblasts (fig. 156, c). The latter may be seen not only 

 under the periosteum, but also passing along with blood-vessels into 

 the Haversian canals. 



Fibres may be seen passing from the deep surface of the perios- 

 teum into the bone the perforating fibres of Sharpey. 



(c.) Observe the lamellae, but their outline is not very distinct, 

 while the canaliculi will not be distinctly visible, being indicated 

 by fine lines traversing the lamellse. The bone corpuscles are 

 nucleated refractive cells, each lying in a lacuna. In such a 

 preparation, one cannot make out that they send processes into the 

 canaliculi. 



(d.) Select a large Haversian canal and study its contents. Note 

 the presence of an artery and vein with very thin walls, and the 

 cavity lined by osteoblasts (fig. 150, Obi.), and the remainder filled 

 ii}) with medullary tissue. 



4. Perforating Fibres. (i.) From a membrane bone of the 

 skull (e.g., the parietal or frontal bone, which has been softened 

 in 2 per cent, hydrochloric acid or in v. Ebner's fluid (p. 37) 



