STRUCTURE AND MULTIPLICATION OF BONE CELLS 141 



6. Place in a watch glass of benzol and carefully scrape off 

 all of the periosteum under a binocular microscope. 



7. Mount in balsam. 



The advantage of Gentian Violet over other stains lies in 

 the fact that bone cells stain very intensely while the matrix 

 remains unstained. The deep stained cells with all their pro- 

 toplasmic processes within the clear white bone gives a very 

 striking picture. The older the bone the greater the contrast. 

 This is probably due to the fact that the bone cells are farther 

 apart and the abundant and more compact bone is less prone 

 to absorb the stain. Among other stains that were used, neu- 

 tral red gave similar results but the contrast is not as great 

 because the cells are not stained as intensely as with Gentian 

 Violet. 



When bone from which the periosteum has been removed, 

 is stained the picture is not as clear. The denuded bone ap- 

 parently^ absorbs some of the dye. With the periosteum in- 

 tact the stain will not diffuse through the osseous matrix. Before 

 attempting to study such sections it is very important that 

 the periosteum be carefully removed. The outer or limiting 

 membrane is easily removed but the inner part of the periosteum 

 is not membranous but more granular and adheres firmly to 

 the bone. It is this inner layer that takes the stain deeply 

 and unless removed obscures the details of the bone itself. 



The bones employed in these investigations were thin lamina 

 from the turbinates and ethmoid bones of both young and adult 

 dogs; the parietal and nasal bones of young cats and rabbits; 

 the parietal bones of mice and rats; thin pieces of young rat 

 femur; and the thin lamina of bone from the human ethmoid 

 and from the walls of the human sphenoidal sinuses. A com- 

 plete series of parietal bones of 15 rats ranging from one to fifteen 

 days old were studied. This series was taken from two litters, 

 one of eight and the other of seven young. Fresh bone was also 

 studied with good results. The refractive indices are sufficiently 

 different to permit one to distinguish between cells and matrix. 

 All of these preparations even the parietal bones of half grown 

 rats and three week old kittens are thin and transparent enough 

 to permit examination with oil immersion lenses. 



