THE TWO GREAT GROUPS OF CONNECTIVE-TISSUE CELLS. 41 



macrophage sister cells, initially gorged with many times the fibroblast quantity. 

 Nothing is perhaps more surprising that the exploration of the skin of an animal 

 which has once been profoundly stained in the typical "acute" dosage and is then 

 permitted to live to a post-experimental period of a half j'ear or more. The macro- 

 phage deposits, originally overwhelmingly more abundant, larger, and more brilliant 

 than those of the fibroblasts, have, except in some paravascular cells, now almost 

 entirely disappeared, even though colorless vacuoles indicate occasionally their 

 former extent. The fibroblasts, on the other hand, may maintain their former 

 dye-content unweakened in brilliancy and are consequently not only the cells now 

 carrying most of the vital dye, but may even seem to be the only cells which pos- 

 sess the latter. We were first acquainted with these facts, to our great surprise, 

 by the examination of the skin of animals which had been permitted to live for 

 relatively long periods after the end of treatment with vital dye. 



Protocol: Rat BH 955, injected intraperitoneally with a 0.5 per cent solution of vital new 

 red, 1916, July 9, 10 c. c; July 23, 29, and August 6, 7 c. c. each day. 



1917, March 1: Light red color shows at base of ears. Subcutaneous tissue generally deep pink. 



Films from the thigh show no differentiation of cell types under the low-power, except where 

 deep-red macrophages outline the capillary walls. The oil shows very fine, dotlike, deep-red 

 granules and colorless vacuoles in macrophages. The paravascular macrophages are filled with 

 round, red vacuoles, but at times show a fading out of some vacuoles, with formation of the small, 

 deep-red granules. Fibroblasts contain medium-sized, round and angular, deep-red deposits. 

 There are smaller granules also in fibroblasts, and some, indeed, have no brilliant, large deposits; 

 great numbers of these cells, however, contain red dye deposits approximately the size of those in 

 the macrophages along blood-vessels. 



In films from the abdomen and side more of the macrophages with large red vacuoles are present 

 out in the tissue away from the blood-vessels. Janus green shows normal mitochondria in both 

 types of cell. 



Protocol: Mouse 57, injected subcutaneously with a 0.5 per cent solution of afridol 

 blue (a deep bluish-purple colloidal dye made by combining 1 molecule diehlor- 

 benzidine with 2 molecules of the H acid, and hence with the formula 



NH 2 OH OH NH. 



-N=N-/ V \-N=N- 



Cl 

 Ma 5 "^ ^-^ SO Na NaO S' " s "" v SO Na 



January 5, 12, 20, 27, February 5, 13, 20, 27, March 6, 13, and 20, 0.2 c. c. each day. 



June 18: Animal is stained a light blue. Under the low-power, films from the abdomen show 

 many cells with a very great dye-content. The oil shows that most of these are fibroblasts whose 

 cytoplasm is packed with fine, bright-blue granules, with an occasional large vacuole; these deposits 

 extend to the limits of the cell's processes, leaving only a narrow zone of cytoplasm (usually next the 

 nucleus) comparatively free from dye. Macrophages escape notice at first on account of their 

 relatively small dye-content. The dye is present in the form of vacuoles varying from an occasional 

 one larger than the nucleus to minute deposits which are possibly concretions within colorless 

 vacuoles. 



Tissue at area of injection is deep blue. Fibroblasts here are packed with dye. The color of 

 the small fibroblast deposits varies from a purple to a distinctly green blue indistinguishable from 

 janus green. Except for a few green-blue "threads" and rods in fibroblasts a. the area of injection, 

 all deposits are vacuolar or round. "Threads" at the injection-site are rare and not striking. 

 They are connected with the vacuolar dye deposits. Macrophages here are more heavily laden than 

 over the abdomen and their vacuoles are deep blue. They contain some fat droplets. Dye deposits 

 are so numerous here as to make study of individual granules difficult, but one is impressed with 

 the similarity of them in all parts studied. 



