THE TWO GREAT GROUPS OF CONNECTIVE-TISSUE CELLS. 45 



phage and fibroblast cells, we have experienced few instances where vital dyestuffs 

 have not displayed with peculiar force the differing phj'siology of these cells. 

 Maximow, indeed, in his last studies, which were with tissue cultures (1916), 

 was able to still identify as fibroblasts the greatly changed, vacuole-filled elements 

 which in old cultures constitute these cells, and his figures are not unlike those 

 which may be found with those vital stains which, we have discovered, easily 

 affect fibroblasts in this way (e. g., T 148). 



This is not a transformation of the whole physiology of these cells. It will be 

 remembered that, under conditions of inflammation, Renaut has seen such striking 

 changes in the fibroblasts as to lead him to declare the assumption of a "rhagio- 

 crine" character on the part of these cells. But it is difficult for us to be certain as 

 to what Renaut would have us infer from such statements. It would appear evi- 

 dent, however, from his account of the development of the connective tissues, 

 that he considers the appearance of a segregation apparatus in fibroblasts in places 

 of inflammation as a reversion to a primitive trait on the part of fibroblastic cells. 

 But we would emphasize, as he does not, that the fibroblasts by this act do not be- 

 come macrophage cells.. We have already shown that a small vacuolar segrega- 

 tion-apparatus normally exists and can be greatly hypertrophied in the fibroblast. 

 Kiyono, who sought to reject our theory of the ingestion of dye on the part of 

 fibroblasts, argued that no instances of the inclusion of foreign material by these 

 cells have been encountered, but they ingest metallic sols, India ink, and even 

 larger particulate matter, so that the act which we term phagocytosis takes place, 

 though admittedly to a lesser degree, in the case of these cells. 



Renaut has also called attention to what he believes to be the more outspoken 

 " rhagiocrine " function of young fibroblasts when compared with adult cells. 

 Indeed, his whole description of the development of the connective-tissue cells 

 indicates that he believes that the ranks of the fibroblasts are continually being 

 augmented by the process of a wandering-in and fixation of macrophage cells which 

 gradually change their character, so that in young animals there are many "rhagio- 

 crine fibroblasts," in old ones very few, throughout the areolar tissue of the body. 



While it might be deemed that our whole study has accentuated in an unmis- 

 takable manner the similarity of reaction of macrophage and fibroblast cells, dis- 

 tinctive differences in this reaction to vital dj^es are never obliterated. Fibroblasts 

 are with some dyes and dosages affected in an identical way as are the macrophages 

 in other cases, but not identically with their own macrophage sister-cells. Our 

 study of the areolar tissues of newborn rats demonstrates that at this time the two 

 distinct cell types are already present and that they behave specifically toward vital 

 and supravital stains. This statement may be made impregnable by limiting 

 it to the affirmation that type segregation is at least true for the overwhelming 

 majority of the connective-tissue cells. 



In the beginning of studies on the living areolar tissue one will repeatedly descry 

 what he believes to be an intermediate cell type and which resembles some of the 

 figures of Renaut. These are best characterized by the statement that certain ex- 



