20 ON THE DIFFERENTIAL REACTION TO VITAL DYES EXHIBITED BY 



Protocol: Rat 100, fed by stomach tube with a suspension of Niagara blue BB in milk 

 (1.5 to 3.0 per cent). November 27 to December 1, inclusive, 5 c. c; December 2, 

 8 c. c; December 3, 7 c. c; December 4 and 5, 10 c. c. each day. 

 December 6: Blue color shows clearly in ears, though stain is not intense. Subcutaneous tissue 

 shows no stain macroscopically. 



Under the oil, macrophages appear as normally, except for the varying content of good-sized, 

 highly refractive vacuoles resembling fat, between which lie bright-blue linear deposits. These are 

 crystals and often lie in bundles of two or more. They are usually apparently free in the cytoplasm, 

 but are also found in all stages relating them to the vacuoles, which in these cases have a brassy pale- 

 red hue. Janus green shows normal filiform and granular mitochondria unrelated to the dye 

 deposits. 



Fibroblasts contain no blue dye. A few of the fat-like vacuoles, smaller than those in macro- 

 phages, are present. Mitochondria as shown by janus green are normal and unre ated to these 

 vacuoles. 



Protocol: Rat 247, fed for 13 days with a 0.25 per cent solution in milk of dye 1824, an 

 isomer of^trypan blue, a pure blue dye obtained by combining in alkaline solution 1 

 molecule o-tolidine with 2 molecules 1.8 amido naphthol 2.4 disulphonic acid, which 

 has the formula 



NH 2 OH OH NH, 



Naq5 rYV" N ^ X )" N " N "T^T S | 5o » Na 



SOjNa 



May 6: The abdominal skin, to the naked eye, can not be said to be stained. 



The oil-immersion shows that both types of cell possess an extremely scanty content of deep- 

 indigo dye deposits which are almost invariably sharp rod-shaped and comma-shaped (figs. 40 and 

 41). In addition, in the macrophages and to some extent in the fibroblasts, there are present 

 extremely faint blue spherical granules. It is worthy of note that the dense deposits of the vital 

 dye in the macrophages are practically identical in morphology with the deposits in the fibroblasts, 

 but in addition in the macrophages there has been a more general faint deposit of the dye in spherical 

 granules of various sizes, some resembling those one sees in a deeply stained animal. They are, 

 in fact, fairly uniform in size. 



We were for a long time disposed to look upon the minute crystalline "dye 

 bodies" produced in the macrophage connective-tissue cells by alimentary dosage 

 as wholly unique and perhaps even related in some obscure way to metabolism. 

 Nor did the secret of their method of production dawn upon us till long afterwards 

 we undertook prolonged, exceedingly dilute administrations of dye by parenteral 

 dosage — the intraperitoneal route. Dye deposits exclusively crystalline in form can 

 also be produced in the fibroblast cells by dosages, still very dilute, but in excess 

 of that required to affect the macrophages alone. In doses sufficient to effect such 

 fibroblast deposits, the macrophage segregation-apparatus will always have been 

 considerably enlarged, though within the vacuoles, crystals or bundles of crystals 

 almost invariably occur, distorting the individual vacuoles into angular, polyhe- 

 dral, diamond-like, or simple fan-shaped structures. 



Crystals also occur in the cells of vitally-stained animals which have been 

 treated in an entirely different manner with some of the vital azo dyes. We would 

 designate these "saturation crystals. " They are produced under conditions of very 

 considerable dosage. The stain in these instances, instead of expressing its effect 

 solely, or almost solely, in crystalline structures, as is the case with "low-dosage 

 crystals," may establish a very extensive vacuolar segregation-apparatus; but, in 



