t4 
il, 
lil. 
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Vi. 
Vill. 
ELEMENTARY HISTOLOGY. 
. The Haversian systems: concentric layers sur- 
rounding the Haversian canals. 
Incomplete Haversian systems: filling up the 
spaces between the complete systems. These 
are the remains of systems which were formerly 
complete but have been removed in part by the 
process of absorption which is continually going 
on in bone. 
The lacune: or spaces in the matrix in which the 
bone cells lie. 
The canaliculi: very fine branching canals connect- 
ing the lacunz together: probably occupied 
while the bone is living by branching processes 
of the bone-cells. 
The large central medullary cavity of the bone: 
occupied during life by the marrow, which 
consists of adipose tissue, with very numerous 
bloodvessels and large nucleated reddish coloured 
marrow cells. 
The peripheral or circumferential lamelle: form- 
ing the most superficial layer of the bone: a 
series of concentric lamelle parallel to the 
surface. 
The perimedullary lamelle: a series of concentric 
lamellz lining the central medullary cavity of 
the bone. 
