THE TWO GREAT GROUPS OF CONNECTIVE-TISSUE CELLS. 13 



greatly in their size as well as in their dye-content. The larger macrophages, which are numerous, 

 contain medium-sized, very regular dye vacuoles. The characteristic cell, however, is one often of 

 great dimensions filled with red vacuoles which vary in size from minute structures to some even 

 larger than the nucleus (fig. 20). Fat globules are numerous in these cells. Neutral red stains 

 the dye vacuoles, forming crescentic concretions in those of medium size. Larger granular con- 

 cretions are present in the large vacuoles. Janus green positive for mitochondria. 



Fibroblasts are well filled with vacuoles of uniform size resembling mast-cell granules and almost 

 entirely round. These are not red, as are the macrophage vacuoles, but have a decided pink color 

 (fig. 21). Linear deposits are so rare as to be discounted. Neutral red stains the dye vacuoles and 

 shows concretions in very many. No linear structures are seen with it. Janus green positive for 

 mitochondria. 



Protocol: Rat 18-2, injected intraperitoneally with a 0.5 per cent solution of dye T 148. 

 January 31 to February 17, inclusive, 1 c. c. each day. 



March 18: Films from thigh examined. Animal is stained deep rose-color. Subcutaneous 

 tissues deep red. Under the low-power, all cells appear packed with pink deposits, among which 

 one can see bright-red concretions even with this power. Macrophages can not be identified. 



Under the oil, macrophages are at first exceedingly difficult to identify, but differ from the 

 fibroblasts in having more round and slightly smaller dye vacuoles, among which crystals, though 

 sometimes present, are never very numerous and are often lacking. If crystals occur in these cells, 

 they are short; and often granular concretions are the only solid form found. The vacuoles are pale 

 pink and colorless (fig. 22). Neutral red affords a method of identifying with certainty the macro- 

 phages, whose abundant vacuoles are stained specifically a bright orange, much deeper, than the 

 staining present in fibroblasts. Janus green shows normal mitochondria. 



Fibroblasts have an enormous number of vacuoles which are fairly uniform in size, are angular, 

 and straw-colored. Among these and occasionally connected with them are straight, deep crimson- 

 black crystals (fig. 23). These are sometimes curved about a vacuole. Crystals are very abundant, 

 the typical cell containing two or three times as many as in the case figured. They are short, 

 straight, almost black rods. There are no other linear deposits. Neutral red stains the vacuoles; 

 janus green shows normal mitochondria. 



March 28: Films of subcutaneous tissue from the upper abdomen show fibroblasts still engorged 

 with small, pale-yellow T 148 vacuoles. While some have no other deposits in them, it is not dif- 

 ficult to find cells with the characteristic dark-red, long, bacillus-like crystals. The majority of 

 the cells display a great number of these. The rods are unconnected with the vacuoles. They 

 vary in length from 11 mm. to 2.5 mm., the average being perhaps 4 mm. or 4.5 mm. Instances 

 of larger crystals in macrophages along the course of blood-vessels are seen, but it is uncommon 

 to find appreciable dye in these cells. 



Again, among the most soluble dyestuffs of this class may be encountered some 



whose speed of egress as well as ingress is so great that, even with relatively high 



dosage, large vacuoles are never created in macrophages, but only small ones, in a 



way similar to that we have just described as following the most dilute possible 



dosage with a typical positive dye. (See figs. 24, 25, 26, 27, 28, 29, 30, 31). 



Protocol: Rat 34, injected intraperitoneally with 1 per cent aqueous solution of Baumwoll- 

 rubin (B. A. S. F.). This bright-red, very diffusible compound has the formula 



Nq0 3 5 n=n-/~~V~Vn=n 



OH 



NaOjS 



April 17, 18, 19, 20, 24, 25, and 26, 4.5 c. c. each day. 



April SO: Animal is stained a rose-color. Skin of thigh is pink. Under the low-power, macro- 

 phages are well filled with pink deposits, while fibroblasts can barely be seen. 



The oil shows macrophages filled with uniform pink vacuoles which are remarkably small. No 

 concretions are present (fig. 24). Janus green is positive, giving a brilliant contrast to the dye 

 vacuoles and remaining positive after the nucleus is stained a light purple, while the vacuoles are 

 orange. 



