THE TWO GREAT GROUPS OF CONNECTIVE-TISSUE CELLS. 15 



The fibroblasts are characterized by the extremely pale dye-content of their small, angular vacu- 

 oles, except where punctate, deep-red concretions occur. Linear structures, though not occurring 

 in all cells, are frequent. These vary from comet elongations of the vacuoles to long, truly fila- 

 mentous structures in the course of which widenings or deep-red concretions may occur. Occasion- 

 ally the concretions in the small vacuoles may take the form of short red rods. The deep-red con- 

 cretions in relation to "threads" are sometimes dispersed along the thread (fig. 29). The dye 

 deposits in the fibroblasts are on the average similar in morphology to those characterizing vital 

 new red, but they are more abundant and they are very much paler in color (so much so that they 

 are overlooked at low power). Janus green stains filiform and granular mitochondria unconnected 

 with the dye deposits. 



Protocol: Rat 19, injected intraperitoneal^ with a 1 per cent solution of dye 1212 d, a very 

 diffusible bright-red dye synthesized for us by combining 1 molecule of o-tolidine 

 with 2 molecules of beta naphthol 8 monosulphonic acid, and hence with the formula 



"■'urOQ" 



°" CH. CH. 



May 3, 6 to 14 inclusive, 16, 18, 20, and 22, 1 c. c. each day. 



May 24: Animal is stained a light pink generally. The skin of the thigh is light pink. Low- 

 power shows macrophages as faint-pink cells. The fibroblasts are not appreciably stained. 



The oil shows that the macrophages, though not enlarged, are full of small, uniform pink 

 vacuoles without condensations or much variation in size, though the form is irregular (fig. 30). 

 Neutral red gives its customary reaction with the macrophages. Janus green gives a specific stain 

 of mitochondria. 



The fibroblasts have a very much scantier content of dye, which consists of fair-sized, angular 

 deposits dispersed in a more scattered fashion and extremely pale pink (fig. 31). Their size compares 

 well with that characterizing the macrophages. Janus green shows normal mitochondria in brilliant 

 contrast to pink dye deposits. 



The abdominal skin is deep red, the macrophages containing very great numbers of small 

 vacuoles which are uniform pink and the fibroblasts containing several times the content of those in 

 the thigh, so that these cells are at length appreciated with the low-power as little trails of granules, 

 but the fibroblastic cytoplasm is still far from filled. 



When, now, we turn to the behavior of negative dyes, i. e., those which have 

 greatly restricted powers of diffusion and remain chiefly in the immediate area 

 where they are injected, the size and number differences in the macrophage deposits 

 vary in strict accordance with the proximity or distance of the cells in question 

 from the injection-point. (See figs. 32, 33, 34.) The macrophages of the subcuta- 

 neous tissue of the head, in animals receiving repeated middorsal subcutaneous 

 dosage with isamine blue (a sulphonated triphenylmethane dye), contain only fair- 

 sized homogeneous globules of the stain, but those near the point of application of 

 the dye and in the area of its immediate spread, after massage, are often gigantic in 

 size. The free peritoneal macrophages of animals which have received intravenous 

 injections of any of these dyes never contain as large or as abundant "dye bodies" 

 as they do on direct injection of the dye into this cavity. We shall refer subse- 

 quently to the fact that quantitative changes to an even more pronounced degree 

 occur in the segregation-apparatus of the fibroblasts under similar conditions, and we 

 have indicated what we feel is the significant import of this evidence for our theory 

 of the similarity in nature of the dye structures in both fibroblasts and macrophage 

 cells. 



