28 ON THE DIFFERENTIAL REACTION TO VITAL DYES EXHIBITED BY 



Protocol: Rat 15, injected intraperitorneally with a 0.5 per cent solution of trypan blue, 

 January 30, February 3, 7, 11, 15, 19, 23, 27, March 3, 7, 11, 15, 1 c. c. each day. 



March IS: Subcutaneous tissue from right thigh examined. Animal is stained a deep blue. 

 Subcutaneous tissues are deep blue. Under the low-power, macrophages appear in sharp contrast 

 to fibroblasts on account of their greater dye-content, although the fibroblasts contain sufficient 

 dye to enable one to outline them under this power. 



Under the oil, macrophages are filled with deep-blue deposits which are most often of the crystal- 

 vacuole morphology. Blue crystals are also present free in the cytoplasm, some of them very light 

 blue. The crystals in vacuoles usually distort them, protruding out for some distance. Neutral 

 red stains the dye vacuoles and modifies the blue color in many of the naked crystals also. It 

 stains some small, round and triangular vacuoles overlooked before between the larger dye vacuoles 

 (fig. 58). 



Fibroblasts contain numerous deposits which are entirely linear, much more delicate than the 

 free crystals in macrophages. There are deep and pale blue crystals of uniform length and thickness. 

 A few fibroblasts may be found with long threads attached to deep-blue deposits and themselves 

 stained faintly. Neutral red stains some small seed-shaped vacuoles not seen before and also 

 stains the paler blue deposits (fig. 59). Janus green shows normal mitochondria in both types of 

 cells. 



Same animal was injected with a 1 per cent solution of dye T 148 intraperitoneal^, March 

 18,4 c. c; March 20, 2 c. c. 



March 22: Subcutaneous tissue from left thigh examined. Animal stained a heliotrope. Under 

 the low-power the skin from the thigh shows many deposits both of blue and red in all cells. Only 

 those macrophages which show large vacuoles can be identified with certainty. 



Under the oil the macrophages are characterized by an abundance of practically uniform-sized 

 round vacuoles, a few of which have blue in them. There are almost invariably a very few larger 

 deep-purple vacuoles containing either amorphous matter or crystals. Some of the smaller vacuoles 

 contain a crystal each. Neutral red gives a somewhat more intense color to the vacuolar system of 

 these cells than with the fibroblasts (fig. 60). 



The fibroblasts are characterized by the lack of much, if any, disturbance with their crystalline 

 trypan-blue deposits. These are usually free in the cytoplasm, although occasionally a pink vacuole 

 can be seen about one. Amongst them are fair-sized, angular, yellow dye T 148 deposits which are 

 on the average slightly smaller than the customary slightly round deposits in the macrophages. 

 Neutral red shows nothing new except an occasional tail to the angular dye T 148 deposits (fig. 61). 



Protocol: Rat 222, injected intraperitoneally with a 0.5 per cent solution of trypan blue. 

 February 25 to March 4, inclusive, 1 c. c. each day. 



March 17: Examined subcutaneous tissue from thigh. Animal is stained a bright blue. Sub- 

 cutaneous tissue is bright blue. Under the low-power, cell types are distinct. Macrophages con- 

 tain an abundance of deep-blue deposits, while fibroblast deposits can barely be seen. 



The oil shows that macrophages contain long blue crystals, free in the cytoplasm for the most 

 part, but occasionally lying within and connected with blue vacuoles. Neutral red stains small 

 vacuoles which have no vital-dye content. It also stains the large vacuoles with crystals and t inges 

 parts of the blue crystals. Neutral red gradually replaces the blue, even on the more deeply stained 

 crystals (fig. G2). 



Fibroblasts contain crystalline deposits which are much smaller than those in macrophages and 

 not as numerous. Neutral red shows great numbers of small vacuoles in these cells. It also stains 

 many of the crystals. 



Same rat was injected with a 1 per cent solution (if dye T 148, March 17, 4 c. c. 



March 19: Subcutaneous tissue of opposite thigh and of abdomen examined. Animal is a 

 dusky reddish violet. Skin of thigh same. Low-power shows macrophages easily evident from 

 their abundance of medium-sized, uniform light-pink vacuoles which crowd the cytoplasm. 



The majority of the macrophages have lost much of their blue deposits and some all of their 

 blue, unless we count a slight bluish tinge in some of the vacuoles. Many instances of small crystals 

 surrounded by a pink vacuole are seen, and these may be interpreted as the most persistent crystals 

 in the cell, the others having been completely dissolved by the vacuole which takes their place. 

 Where the blue was previously in a large, dense vacuole this remains with no change except a 

 violet blue from some T 148 contamination. Many cases are seen of cells which contain but two or 

 three blue vacuoles, while the remainder are pink. Along blood-vessels in the thigh the blue' 

 crystals are apparently unaffected, but there are in addition in these cells a considerable number of 

 small pink vacuoles (fig. 63). 



