430 



MOVEMENTS 



lacunae measure ^Vo to For of an incn ( 2O to 3 ^) ^ n ^eir lon 

 diameter, by about 2sVo ^ an mcn ( IO /*) * n width. 



Canaliculi. These are little wavy canals, connecting the lacunas 

 with each other and presenting communications between the first series 

 of lacunae and the Haversian canals. Each lacuna presents eighteen 

 to twenty canaliculi radiating from its borders. The length of the can- 

 aliculi is ^5- to -^ of an inch (30 to 40 /A), and their diameter is about 

 2"5Wo f an mc h /*) The arrangement and relations of the Haversian 

 canals, lacunae and canaliculi are shown in Figure 88. 



Bone-cells, or Corpuscles. These structures are stellate, granular, 

 with a large nucleus and several nucleoli, and of 'exactly the size and 



Fig. 88. Vascular canals and lacuna seen in a transverse section of the humerus, x 200 (Sappey) . 



I, i, i, section of the Haversian canals; 2, section of a longitudinal canal divided at the point of 

 its anastomosis with a transverse canal. Around the canals, cut across perpendicularly, are seen the 

 lacunae (with their canaliculi), forming concentric rings. 



form of the lacunae. They send out prolongations into the canaliculi, 

 but it has been impossible to ascertain positively whether or not they 

 form membranes lining the canaliculi throughout their entire length. 



Marrow of the Bones. The marrow ,is found in the medullary cav- 

 ities of the long bones, filling them completely and moulded to the irreg- 

 ularities of their walls. It is also found filling the cells of the spongy 

 portion. In other words, with the exception of the vascular canals, 

 lacunae and canaliculi, the marrow fills all the spaces in the funda- 

 mental substance. The cavities of the bones are not lined with a 

 membrane corresponding to the periosteum, and the marrow is applied 

 directly to the bony substance. In the foetus and in young children 

 the marrow is red and very vascular. In the adult it is yellow in some 



