84 PRACTICAL HISTOLOGY. 



cover-glass requires to be removed and finally mount in 

 glycerine jelly ; glycerine renders the bone corpuscles too 

 transparent. If, however, the section be stained with 

 picro-carmine, examine, and preserve it in Farrants' solu- 

 tion, glycerine, or glycerine jelly. 



(L.) The compact and spongy bone. If the section be 

 through the central part of the shaft of the bone, little cancel- 

 lated tissue will be seen. The Haversian systems each 

 consisting of a Haversian canal, with a concentric series of 

 lamellae are seen divided transversely. The systems are 

 of somewhat irregular shape, and the Haversian canal is 

 often placed eccentrically. This results from the substance 

 of the system growing from the Haversian canal outwards, 

 most rapidly in the direction of least resistance. Under 

 the periosteum the lamellae have a direction parallel with 

 that membrane. Between the Haversian systems there are 

 small sets of lamellae, that are generally more or less 

 parallel with the direction of the sub-periosteal lamellae. In 

 the development of the bone the lamellae produced around 

 the Haversian canal grow outwards, and cause the par- 

 tial, and in some places the complete, absorption of those 

 lamellae parallel with the periosteum, and originally pro- 

 duced from it. The lamellae and the bone corpuscles will, 

 however, be more clearly seen with H. 



(H.) The bone corpuscles. Nucleated masses of proto- 

 plasm in branching spaces, the lacunae and canaliculi. The 

 last are difficult to see in softened bone, unless it be stained 

 with picro-carmine. The wall of the lacunae and canaliculi 

 consists of a homogeneous calcified membrane that may be 

 detached from the lamellae, although with difficulty if 

 softened bone be teased with needles. (Virchow.) 



b. The lamella. Examine them in a Haversian system. 

 Five or six lamellae usually intervene between two neigh- 

 bouring lacunae. The elliptical shape of the lacunae 

 apparently results from compression between the lamellae. 



c. Sharpens fibres may be found perforating the sub- 

 periosteal lamellae. They are calcified fibres that run from 

 the periosteum inwards between the Haversian systems. 

 They are not found within the latter. Remove the cover- 



