THE TWO GREAT GROUPS OF CONNECTIVE-TISSUE CELLS. 35 



by the occurrence of these mammoth blue vacuoles in small cells which are apparently macrophages, 

 but which contain no greater actual number of dye deposits than the fibroblasts, if, indeed, they 

 contain as many (fig. 76). 



Under the oil the identification of macrophages is confirmed. They are rather small, rounded- 

 up cells, varying in size and dye-content somewhat, but typically containing about a dozen very 

 large vacuoles and also more numerous small vacuoles and a varying number of crystals free in the 

 cytoplasm. The large vacuoles are deep blue and show all stages of crystallization of their dye- 

 content; some are colorless, with blue crystals included. Small fat vacuoles are present also. Neu- 

 tral red stains the vacuoles which are relatively free from the blue dye. In cells which are full 

 of crystals the blue needles remain side by side with numbers of bright-red vacuoles. The crystals 

 are then apparently free from vacuoles. Areas distant from the puncture-point and abdominal skin 

 show a great preponderance of crystalline deposits in macrophages. The crystals are long and 

 deeply stained and so numerous as to form "brush-heaps "in the cytoplasm. Janus green, 1:10,000 

 stains short mitochondrial rods and granules between the dye vacuoles. 



Fibroblasts on the abdomen are filled with dye deposits which, while usually linear, are also 

 vacuolar. The cells all over the body show a maximum reaction to the dye; syncytial masses are 

 formed with two and three nuclei. The vacuoles when present are small and less deeply stained 

 than the linear deposits, so that the deep-blue crystals and curved threads are the most striking part 

 of the picture. Elongated triangles and comets are found also. The long threads, stained blue 

 usually, but also colorless, are very numerous, especially in areas more distant from the puncture- 

 point, and form amazing tangles in the cytoplasm. Neutral red, in films from the abdomen, stains 

 the less deeply blue linear deposits and also the vacuoles, which are often almost as numerous as the 

 crystals. In other areas where the deposits are all linear the parts of the crystals which are less 

 deeply blue are stained red with the supravital dye. In these fibroblasts very few vacuoles reacting 

 to neutral red are present, so that the cells appear almost wholly blue, even with neutral red. Janus 

 green, 1 : 10,000, apparently brings out additional structures whose color and morphology are indis- 

 tinguishable from the linear dye deposits. 



That the crystals which we have observed in both types of cell do not represent the 

 tingcing either of preformed or newly risen protoplasmic crystalline structures, such 

 as occur naturally in some body-cells (e. g., Sertoli cells), would appear to be quite 

 conclusively proven by the fact that there is a specificity of the crystal form for each of the 

 varying crystallizing vital dyestuffs employed. We instance here the blue needles of 

 trypan blue (figs. 74, 76), the long, pointed saffron needles of dye 245 (fig. 42), 

 the amethyst prisms of dye 226 (figs. 77, 78, 79, 80), the rhomboidal plates of tri- 

 sulfonazoblau (fig. 81), and the deep-red rods of T 148 (fig. 23). 



4. The evidence furnished by "double-staining" experiments with two dye- 

 stuffs of the azo series, most beautiful when the dyes vary both in color and in the 

 manner of deposition in the cell, is easier to follow in the thin, expanded fibroblasts 

 than in the macrophages, and the data which we have presented under this heading 

 for the macrophages are all duplicated by the performance of the fibroblast cells 

 (figs. 44, 46, 49, 52, 53, 55, 56, 59, 61, 64). 



The foregoing cytological evidence would now appear to amply justify the 

 following statements : 



1. The mitochondria of fibroblasts are not to any considerable extent "used 

 up, " even if they are in any way concerned in the phenomenon of the establishment 

 of vital-dye deposits in the fiber-forming cells. 



2. The "dye bodies" of fibroblasts represent actual accumulations in fluid, 

 high colloidal, flocculated, or crystallized form of the actual dye substance used in 

 the tests. 



3. There is thus an identity in nature of at least the majority of the "vital 

 structures" produced by azo dyes in the protoplasm of the fiber-forming and in 

 the great phagocytic cells. 



