148 T. H. BAST 



Both in and between the lamellae are many small ovoid spaces which 

 are partially filled by small flattened cells, the bone cells; these spaces 

 are known as lacunae. From each lacuna minute canals, the canaliculi, 

 radiate in all directions, thus placing the lacuna in open communication 

 with its neighbors, and eventually with the lymph spaces of the central 

 Haversian canal. The branching processes of the bone cells frequently 

 project for a short distance into the canaliculi. These cytoplasmic 

 branches are more numerous in newly formed bone, later they are 

 retracted and the cells become more or less shriveled in appearance. 



These two accounts typify in general the accounts given in 

 other texts of Histology. Such views are based on preparations 

 of decalcified bone. The picture by Joseph of a bone cell partly 

 filling a lacuna is taken by most authors as the ideal. 



a. Relation of cells to lacunae and canaliculi 



The view that the bone cells partly fill the lacunae and that 

 the canaliculi are for the most part empty is also held by Schaffer. 

 In his textbook of Histology, he refers to Joseph's picture as 

 a typical example. He says, ''The cell almost fills the lacunae 

 and may send processes through the canaliculi to anastomose 

 with neighboring cells." It is interesting, however, to note 

 that in commenting on Virchow's statement that the capsules 

 of bone cells were homologus with those of ordinary connective 

 tissue cells, he remarks, "To this may be added that the en- 

 closing lacunae and canaliculi are to be looked upon as corres- 

 ponding to the cell-space of that tissue." Ranvier thinks that 

 the canahculi are hollow tubes. Ch. Robin writes that processes 

 extend nto the canaliculi in primitive bone but that in old 

 bone the canaliculi are empty. In Keibel and Mall, Bardeen, 

 whose observations were on embryonic tissue, states, "The en- 

 doplasmic units, or bone corpuscles, have branched processes 

 which anastomose freely through the canaliculi with those of 

 neighboring cells." Renaut presents results which affirm the 

 theory of protoplasmic continuity. He fixed bone in alcohol 

 and also in osmic acid fumes and decalcified in chromic acid 

 or picric acid. In such preparations he found that most lacunae 

 were filled by the bone cells. He obtained his best results with 

 the operculum of Cyprins which he fixed in alcohol, decalcified 



