THE TWO GREAT GROUPS OF CONNECTIVE-TISSUE CELLS. 7 



tant categories of these cells occur, viz, the endothelial macrophages of the liver, 

 lymph-glands, bone-marrow, and spleen, and the free macrophages of the peritoneal 

 and other serous fluids. In the areolar tissue by far the greater bulk of the vital 

 stain has affected these connective-tissue macrophages. They are the cells par 

 excellence which are electively displayed by this method. Almost every possible 

 size of spherical dye-bodies or granules frequently occurs, varying from those on the 

 limits of visibility up to structures as large or larger than the nucleus. The greatest 

 disparity in sizes of these "seats" of the vital-dye effects occurs when the dye 

 administration has been rapid and the dosage large (maximum acute effect); but a 

 prolonged low dosage, though not the lowest, may render them strikingly uniform 

 in dimensions. We shall designate these structures as the segregation-apparatus of 

 these cells. They correspond to the vacuoles and "grains de segregation" of 

 Renaut, the "granules" and "vacuoles" of Lewis and Lewis, and the "chondrio- 

 somenapparat " of Tschaschin. We believe we can show them to be a mechanism 

 elaborated under functional stress for the temporary storage of these compounds. 

 The fibroblasts, larger, thin, flattened, almost perfectly transparent elements, pos- 

 sess in their cytoplasm, otherwise glassy-clear, 1 a segregation-apparatus so different 

 from that of the macrophages that it has been misunderstood and wrongly identified 

 with the mitochondria by Tschaschin. 2 Suffice it to say that the fibroblastic vital 

 deposits of dye are always more minute and less perfectly spherical than those 

 characterizing the macrophages, and that in the case of most dyes these minute 

 deposits are often linear in morphology. (See figs. 73, 1, 2, 3, 4.) 



Protocol: Rat 10, injected intraperitoneally with aqueous solutions of 0.5 per cent trypan 

 blue, the combination, now well known, of o-tolidine with 2 molecules of the 1.8 

 amido-naphthol 3.G disulphonic acid (H acid). March 1 to 7, inclusive, 2 c. c. each 

 day. 

 March 7: Animal is deeply stained. Under the low-power, macrophages appear filled with 

 bright-blue deposits, while fibroblasts can barely be seen as containing fine blue granules (fig. 1). 

 Under the oil, identification of cell types is confirmed. Macrophages have numerous bright- 

 blue deposits which are practically all vacuolar. Crystals of dye occur rarely. Fibroblasts have 

 fairly numerous, typical, minute deposits which tend to be linear, but are not the elongated thread 

 and crystal forms found in chronic stains. 



Protocol: Rat 31-2, injected intraperitoneally with fresh aqueous solutions of 1 per cent 

 trypan blue, February 8, 11, 14, and 17, 1 c. c. each day. 



February 19: Animal is stained a deep pure blue. Under the low-power, cell types can be 

 distinguished. 



Under the oil, macrophages are distinguished by their more abundant dye content and vacuolar 

 structures, which vary greatly in size and in many of which crystals are condensing (fig. 3). Neutral 

 red (1:5,000) gives a specific reaction with the vacuolar segregation-apparatus. It shows that the 

 vacuoles have sickle-shaped accretions along one edge and that as a rule few or no crystals free in 

 the protoplasm occur. Instances of their protrusion from vacuoles are, however, occasionally to 

 be seen. Janus green (1:5,000), exposed 30 seconds and covered, showed undoubted mitochondria. 



The fibroblasts in fresh preparations are characterized by minute deposits. Where the color 

 is deep blue it is evident that these are crystals, but there are also many other minute, faint blue 

 deposits which as a rule have an angular morphology. Neutral red brings out more clearly the 

 fainter cytoplasmic deposits which before the counterstain was applied were not appreciated 

 (fig. 4). No filar structures are encountered. Janus green (1 : 10,000), 3 minutes, showed a normal 

 mitochondrial apparatus in the fibroblasts without staining the neutral red bodies. 



1 This is not quite true, since the filiform mitochondria of these expanded cells can always be distinctly seen by virtue 

 of their difference in refractive index from the remaining protoplasm. 



1 Indeed, leading even to the derivation of the macrophage segregation-apparatus from mitochondrial 





