STRUCTURE AND MULTIPLICATION OF BONE CELLS 149 



and delaminated. In this way he was able to see the relation- 

 ship of cells within the lamina. Apparently he got results from 

 the decalcified, delaminated operculum similar to those obtained 

 from the thin bones of man, dog, cat, rabbit, rat and mouse 

 which were subjected to no chemical treatment except alcohol 

 fixation. Retterer realized that acid treatment of bone des- 

 troyed the actual structure of the cell. He made various at- 

 tempts to overcome this. He studied small fragments in glycer- 

 ine and then compared them with sections properly fixed. He 

 observed that the cells and processes completely fill the cavities 

 in the bone. With his description of the structure of the cell, 

 however, I am not able to agree. He found that the central 

 portion of the cytoplasm is dense containing a large amount 

 of chromatin while the peripheral portion is clearer with some 

 strands of chromidial substance radiating from the central por- 

 tion. Such pictures are common in total bone preparations 

 which have been scraped or also in chips of bone. However, 

 they are always found at the surface where air and fluids came 

 in direct contact with them or sometimes in cases of improper 

 fixation. Such pictures give the impression of protoplasmic 

 coagulation or shrinkage. In fresh bone examined in normal 

 salt solution or in well preserved cells the picture is always hke 

 that shown in figure 3. 



5. Multiplication of bone cells 



In Lewis and Stohr's textbook of Histology we read, '' Ap- 

 parently bone cells do not divide." Haour tells us that bone 

 cells degenerate but he says nothing of their multiplication. 

 Apparently Schaefer did not beheve in bone cell division for 

 he writes, ''The canihculi, which are at first short, are after- 

 wards extended by absorption so as to anastomose with those 

 of neighboring lacunae." If cells came from a mother cell but 

 never completely separated then the protoplasmic or canilicular 

 connections would be present from the beginning of bone for- 

 mation. Bonome claims that under certain conditions where 

 a rich supply of blood is present, bone corpuscles may give 

 rise to osteoblasts. Bonome made his observations on regen- 



