22 ON THE DIFFERENTIAL REACTION TO VITAL DYES EXHIBITED BY 



show in general that the places for the reception of these substances are not spe- 

 cific. The compounds in question,- though differing in color, are indeed so near 

 alike that it would be surprising if they were segregated in their manner of deposi- 

 tion in the cell. The phenomenon is, of course, entirely different from the meta- 

 bolic segregation of substances occurring, for instance, in plant cells, where the 

 plastids for the reception of starch do not contain chlorophyll, and vice versa. 



Far more crucial are the experiments made with dye substances which differ 

 not only in color, but also in the rate and form in which they are segregated in the 

 cell. If the second substance is a crystallizing substance (like trypan blue), its 

 employment as a second dye in such a series of experiments can be detected, not 

 merely by blue contamination of some of the pre-existing red vacuoles, but also by 

 the angular or seedlike distortions of these structures which its crystals provoke. 

 (See figs. 44, 45, 46, 47, 48.) 



Protocol:} Rat 19-2, injected intraperitoneally with a 0.5 per cent solution of dye T 148, 

 January 31, February 5, 10, and 15, 4 c. c. each day. 



March 27: Subcutaneous tissue of right thigh examined. Animal stained a bright pink. Skin 

 of thigh light pink. Under the low-power all cells are seen to carry pale-pink vacuoles, the macro- 

 phages being distinguished with certainty along the blood-vessels only, where concretions are more 

 pronounced. 



Under the oil, cell types can be differentiated. The macrophages contain watery vacuoles 

 which show slightly more color than those in the fibroblasts and are more irregular in size and less 

 closely packed. Neutral red 1 : 10,000 distinguishes the macrophages everywhere, because of the 

 deep orange tint assumed by these vacuoles. In addition, much deeper staining concretions are 

 present in many of the vacuoles (fig. 44). 



The fibroblasts are distinguished by the possession of enormous numbers of quite uniform- 

 sized deposits in which the color is only a pale yellow. With neutral red these assume a uniform 

 pink, which is very much beneath the intensity of the vacuoles of the macrophages. Occasional 

 instances of the characteristic rod-like crystals of this dye are seen. These do not appear to be 

 related to vacuoles, but to lie between them. 



Janus green gave a positive reaction for both types of cell. It is particularly interesting to 

 see the mitochondrial apparatus in the fibroblasts which are already gorged with dye deposits. 

 They are diffusely distributed throughout the protoplasm, little groups of them sometimes occurring 

 where the dye deposits are relatively less abundant and also occasionally along very delicate strands 

 of almost transparent protoplasm in which dye deposits are absent. The ease with which the 

 mitochondria can be demonstrated in the macrophages where they are seen first is remarkable. 



Same animal injected with a 0.5 per cent solution of trypan blue, March 28, April 1, 3, 7, 

 9, 13, 15, 18, 21, 24, 27, 30, May 3, 6, 9, 12, 14, 10, 18, 20, 22, 24, and 26, 1 c. c. 

 each day. 



May 27: Subcutaneous tissue from left thigh examined. Animal stained a deep blue. Sub- 

 cutaneous tissue deep blue. The low-power shows that the macrophages alone have enough dye 

 to be seen, but in them the dye is in the form of small, elongated, dense-blue deposits, so as to make 

 brilliant display. 



The oil shows the macrophage deposits to be almost exclusively crystalline. Neutral red 

 1 : 10,000 stains seed-shaped structures in the macrophages, where the blue content was previously 

 very faint, and so intensifies the reaction of these cells (macrophage reaction) (fig. 45). 



The fibroblasts remain full of very small, now almost colorless vacuoles produced by the 

 previous dye treatment. A considerable number of the vacuoles, but by no means half of them, 

 house a single minute blue crystal or, in rare instances, a sheaf of crystals of trypan blue. Several 

 apparently free crystals are also found (fig. 40). With neutral red 1:10,000 the color in the 

 fibroblasts is an extremely pale vermillion, so that it can not lie seen with the low-power. 



The case shows that there has been greater difficulty in the lodgment of the trypan blue in the 

 fibroblasts than would be the case in a previously untreated animal, for there are fewer of these 

 than we would otherwise see; furthermore, the blue crystals are minuter structures than would 

 otherwise occur with this dosage. They are probably in all cases lodged in the T 148 vacuoles and 



