DEVELOPMENT AND FUNCTION OF MACROPHAGES IN BONE-REPAIR. 



carefully sutured with sterile silk, and the most rigid asepsis was observed through- 

 out. In the same animals, before recovery from the anesthetic, the tibia and femur 

 of the left hind leg and a few of the ribs on the left side were fractured. No attempt 

 was made to splint the bones, so that healing took place under the same conditions 

 as in natural life. 



There were slight variations from this general type experiment; in some 

 animals only trephining was done and in others only fracturing. In all, 20 animals 

 were used, which furnished 16 trephined skulls, 15 fractured tibiae, 15 fractured 

 femora, and 12 sets of fractured ribs. In table 1 a full description of the material 

 is given. 



TABLE 1. Material. 



se = specimen examined. 



The animals were killed at various periods during the repair process, the 

 specimens ranging from the second to seventy-first day of healing, as shown in 

 table 1. The vital-staining technique was the same as that used by Shipley and 

 Macklin (19 16 1 ' 2 ) in their work on developing bone. Shortly before the time selected 

 for killing, trypan-blue was administered intraperitoneally in the form of a sterile 

 1 per cent aqueous solution. As a rule, the dyestuff was given 48 hours before 

 killing and repeated after 24 hours, so that the macrophages were exposed to its 

 action for 2 days. Occasionally the period of exposure was as short as 1 or as long- 

 as 3 days. No ill effects followed the exhibition of the dye. 



