518 J. T. IRVING AND C. S. IIANDELMAN 



Group 3. Animals were treated similarly to those of group 2, 

 but the bone was decalcified and implanted 2 weeks after removal. 

 Groups of 4 or 5 animals were killed 1 to 3 weeks later. 



Group 4. Pieces of muscle or skin were removed from normal 

 animals and treated with EDTA for the same length of time as the 

 bones in group 1. After implantation, 4 animals were killed weekly 

 up to 4 weeks later. 



Group 5. Animals had bacterial agar hydrocolloid implanted 

 under the skin. Four animals were killed weeklv up to 6 weeks later. 



Group 6. This part of the experiment is in a preliminary stage. 

 Decalcified and devitalized bone implants were used. Parathyroid 

 extract (100 units, TOO gm bodv weight for 4 days) was adminis- 

 tered to some of the animals before the implants were removed, and 

 other animals were parathvroidectomized with a cautery just prior 

 to bone implantation. Groups of 4 rats were killed at intervals up to 

 8 weeks. 



Results 

 Group 1 



Decalcified bone had been deliberately chosen for the study of 

 the giant cells, since it was possible to cut the specimens without 

 further decalcification and thus better preserve enzyme and morpho- 

 logical details. The morphology and number of giant cells were the 

 same as was found around devitalized calcified bone. All implants 

 were completely devitalized as judged by empty osteocyte lacunae. 

 They were also completely decalcified before implantation, as shown 

 by analyses of the reference sections. None of the implant sites be- 

 came septic, and this applied to all the implants in all groups. 



There was a strong small-celled reaction around each implant 

 early in the experiment. This became less intense with time, and 

 later a fibrous capsule surrounded the implant. After 1 week multi- 

 nucleated cells could occasionallv be seen around the bone, occur- 

 ring specially at the sectioned ends. By 2 weeks man\' more were 

 seen, and to judge from slide counts, the number was maximal at 



