30 



DEVELOPMENT AND FUNCTION OF MACROPHAGES IN BONE-REPAIR. 



the first 10 days following the wound. In association with this gradual removal of 

 the waste material there was a marked increase in macrophages of large size and 

 pronounced staining abilities, extending from the sixth to the ninth day; after this 

 the phagocytes became less conspicuous and had reached almost their normal 

 condition on the twelfth day. Though not plainly seen on the third day in the 

 cleared skull they were abundantly present in the sections of this, so that the 

 period of macrophagic activity extends from about the third to the tenth day 

 inclusive. Probably they begin to increase, as in the ribs and long bones, before 

 the third day. 



The cleared skulls present one or two minor points of difference as compared 

 with the ribs. The debris, as the table shows, disappears somewhat more slowly, 

 and this is associated with a longer duration of the macrophagic tissue. To explain 

 this slowness of absorption we have to consider, in one skull (S5-1), the element of 

 infection. Again, macrophages are never quite so abundant in the skulls as in the 

 ribs and are perhaps a little slower in their mobilization. 



TABLE 2. 



The plus signs indicate roughly the relative amounts of debris or macrophaaic tissue, as the case may be. Thus + 

 would denote a discernible increase in macrophages a^ compared with the normal, or the presence of an appreciable amount 

 of debris; 4- 4- + + would mean an exceptional amount of macrophagic tissue or del iris, etc. The sign indicates an absence 

 of debris or macrophages, as the case may be. The sign means that no evidence is presented by the specimen. The 

 bracketed signs indicate micropha?ei which have persisted in regions where formerly tissue was being absorbed. They are 

 comparatively small and weakly staining. 



The sections of the long bones show even more strikingly the same remarkable 

 coexistence of debris and abundant macrophagic tissue over a period from the 

 second to the tenth day, with macrophages remaining in the field in reduced amount 

 as far as the thirtieth day. 



In the sections of the skull the same parallelism of debris and macrophages is 

 found, extending (in the specimens examined) from the third to the tenth day. 



From this summary, the results of which are graphically set out in table 2, it 

 is evident that the occurrence of excess of macrophage-tissue is strikingly syn- 

 chronous with the presence of waste material. Following rapidly upon the injury, 

 macrophages become excessive in numbers in and around the damaged tissue; 

 these cells are not only larger in size than the usual resting macrophages, but are of 



