THE TWO GREAT GROUPS OF CONNECTIVE-TISSUE CELLS. 31 



tend to combine with the basic dye (janus green 1:100,000 to 1:10,000). The 

 simple scheme of the employment of higher concentrations of the mitochondrial 

 dye (janus green 1 : 5,000) over a long period of time (2 to 5 minutes) has sufficed 

 to accomplish in these acid-dye-soaked cells a specific result. But the janus re- 

 action can be secured in its usual specific way and by more usual methods if, after 

 the attainment of the vital-azo stain, a considerable time is allowed to elapse so 

 that the azo compound is not present in appreciable quantities, except in the actual 

 segregation-apparatus of the stained cells. By either of these two means normal 

 mitochondria can be demonstrated after the most various dosage and with the most 

 various dyes of the acid-azo series (figs. 5, 16, 37, 67, 69, 70, 71). In spite of the 

 striking similarity in morphology, number, and distribution of the vital "dye 

 bodies" and the mitochondria in fibroblast cells, we rest our ability to discriminate 

 between these structures on repeated experiments with the living cells which may be 

 summarized as follows : 



SEGREGATION APPARATUS. MITOCHONDRIAL APPARATUS. 



The segregation-apparatus is eleetively stained by freshly Mitochondria are not electivcly stained by any con- 

 made isotonic solutions of neutral red 1 : 10,000 and centration of neutral red. 

 other basic dyes. 



The segregation-apparatus is not stained by concen- Mitochondria are eleetively stained by appropriate 



trations of janus green B which are elective for concentrations of janus green B in isotonic salt 



mitochondria. (1:100,000 to 1:10,000, and under certain con- 

 ditions 1 : 5,000). 



When the segregation-apparatus is stained by solutions Specific janus-green stains of the mitochondria fade 



of janus green in excess of strengths specific for rapidly and completely after a short interval, in 



mitochondria, the stain remains, except for partial which the dye is reduced to a pink form (diethyl- 



reduction, for a more considerable interval of time. safranin). 



The morphology of this system does not change on long The morphology of this system changes conspicuously 



standing; preparations 24 hours old are often not within several minutes, segmentation, swelling, or 



appreciably changed. dissolution effects supervening. 



It is interesting that in some instances, after extensive treatment with the 

 acid-azo dyes, the mitochondria of fibroblasts occasionally occupy distinct cyto- 

 plasmic zones rather free from dye deposits (fig. 70). Usually, however, the mito- 

 chondria are not greatly disturbed in their arrangement, tending to be diffusely 

 scattered, except for the invariable presence of some of them near the nuclear mem- 

 brane; and this is true even with the employment of those vital dyestuffs which we 

 have discovered to create a large segregation-apparatus in these cells. In the case 

 of animals 19-1 and 24-1 (figs. 71 and 5), the mitochondria of the fibroblasts are 

 eleetively displayed amongst the characteristic numerous large A r acuoles created 

 by dye T 148. It is apparent, then, that most of the dye deposits in the fibro- 

 blasts are not mitochondrial in nature, even though they have special characteristics 

 (minute size and form) which would justify all but the most critical observation in 

 aligning them with mitochondrial forms. 



We desire to refer briefly now to an actual tingeing of the mitochondria of 

 fibroblasts with acid-azo dyestuffs, in cases where the vital dye is in considerable 

 concentrations. We have been able to satisfy ourselves, in cases of high intra- 

 peritoneal dosages, of the existence of fibroblasts in the areolar tissue of the abdo- 

 men, where the mitochondria are clearly but faintly tinged with the vital dye. 

 This is probably a transient effect. It may be also a necrobiotic one, for other cells 



