The Two Faces of Resorption 3 



JowsEY (1963) and Jowsey et al. (1964) have reported on the basis of micro- 

 radiographic studies of a variety of bone depleting conditions, "that the osteocytes 

 may be capable of controlling the amount of mineral and also perhaps, the amount 

 of matrix, deposited in the tissue adjacent to them". At the Second Parathyroid 

 conference held at Noordwijk in August 1964, Talmage (in press) who had already 

 demonstrated that the removal of hydroxyproline from bone followed a pattern 

 quite similar to that of the mineral components (Talmage, 1962), reported that 

 numerous enlarged osteocytes were observed early in bone fragments cultured with 

 parathormone. 



2. Electron microscopy of bone cells of the chick 



Further aspects of this osteocytic activity have been uncovered by electron micro- 

 scopy during the past year. 



Very intense osteolysis has already been observed in the bones of young chicks 

 (Belanger et oil., 1963 b). This type of material being not too hard, can be processed 

 for electron microscopy with a minimum of pretreatment. 



In collaboration with Teruhiko Semba and Susan Tolnai, small fragments of the 

 mid-diaphysis of the tibia from II days chick embryos were fixed in Palade's isotonic 

 osmic mixture at 5 °C and then partly demineralized in an aqueous isotonic solution 



