32 ON THE DIFFERENTIAL REACTION TO VITAL DYES EXHIBITED BY 



in the same neighborhood show toxic effects of the dye (c. g., nuclear staining). 

 We have seen no evidence of the participation of these tinged mitochondria in the 

 formation of the granular or vacuolar deposits of dye. Levi (1916) has reported 

 mitochondrial tingeing in the case of fibroblasts of tissue cultures cultivated in 

 pyroll blue plasma and jumps to the conclusion that he has verified Tschaschin's 

 claim that the fibroblastic dye bodies are mitochondria. Before Levi's paper 

 appeared, similar results in tissue cultures were repeatedly secured by M. R. Lewis, 

 and we have had the privilege of seeing these indisputable preparations. This 

 evidence docs not, in our estimation, establish even the mitochondrial origin of 

 fibroblastic dye deposits. It certainty could not enable one to declare that the usual 

 dye bodies shown by fibroblasts, after treatment with these dyes, represent an elec- 

 tively stained mitochondrial apparatus. 



We have previously refrained from describing still other characteristics of the 

 kind of deposits which are frequently produced in these cells and which are, even 

 more strikingly, so like mitochondria as to further justify this confusion. We refer 

 to the greater tendency of the fibroblast to exhibit linear forms in its segregation 

 apparatus, due either to the minute rod-like and needle-like crystals which form 

 in these cells or to the production of characteristic "thread bodies," which we will 

 describe later, but which, by all stages of transition, can be seen to belong to the 

 segregation-apparatus and not to the mitochondria of these cells. The description 

 of these phenomena, which are highly characteristic for the fibroblasts, must be 

 deferred until we have established the nature of the "dj'e bodies" in fibroblastic 

 cells by the same four lines of evidence which we have employed in the case of 

 the macrophages and which speak even more conclusively for the d3 r e-storage 

 hypothesis of the "vital bodies" present in fibroblasts, though this deposition is 

 greatly modified by the characteristic physiology of these particular cells. 



1. A normal minute vacuolar segregation-apparatus is not lacking in fibro- 

 blastic cells (fig. 13). It is distinguished, however, by its insignificant develop- 

 ment, shown by the small size and number of vacuoles when compared with those 

 always present in the macrophages, and by the greatly lessened reaction of those 

 bodies to supravital neutral red (1:10,000). In fact, only by the employment of 

 neutral red can the almost glassy-clear protoplasm of normal fibroblasts be made 

 to exhibit its low content (5 to 25) of the minute, punctate, granular, or small vacu- 

 olar structures for which we regard this dyestuff (in harmony with Dubreuil, 

 Renaut, and M. R. and W. H. Lewis) as a specific test. This inconsiderable seg- 

 regation-apparatus of the fibroblasts can be greatly modified by various methods 

 of staining with acid-azo dyes. The greater variability in the extent of the appa- 

 ratus normally characterizing the macrophages might tend to make some of our 

 assertions about the exact dependence of the morphology of this system on the 

 amount of dye dosage less certain than need be the case with fibroblasts; for it is 

 possible in the fibroblasts to obtain a most complete array of quantitative data. 

 Although we have described the usual scanty content of these cells in "dye bodies," 

 the number and size of the latter speedily increase with increased dye dosage in the 



