Development, &g., of the Fat-cell. Bij G. and F. E. Eoggan. 355 



This task proves much simpler than might have been expected, 

 considering the opposite opinions held on the subject, partly owing 

 to the modifications we have introduced into methods of preparation 

 of tissues for examination, and partly because we find that the 

 opposite opinions referred to are due principally to the fact that 

 observers have regarded the same cell element from difierent points 

 of view, in difierent shapes, and under different aliases ; so that, 

 while those who have examined it from the front have insisted that 

 the fat was first developed in a flat or round cell, those who have 



iuiLedded in a granular matrix, unlilje that in Fig. 5, which is transparent and 

 had not retrograded so far as in this figure, a, a. Exhausted and granular fat- 

 cells in which fat has been re-deposited, h. Similar cell, from which some of 

 the fat has been extruded, but its protoplasm, having been previously fixed by 

 silver and osmic acid, has not contracted, c. Granular cells which had under- 

 gone exodus, but to which the granules have returned, d. Wandering cell. 

 Preparation stained with logwood. 



Fig. 12. — Preparation from a rat which died of old age, showing a mass of 

 fat-eells undergoing granular exodus and moving off f*t )«ass6'from the bed where 

 they had been formed, a. Wandering cell. h. Exhausted fat-cells which have 

 not undergone granular exodus, c, c. Fat-cells undeigoing granular exodus and 

 moving off en masse. Preparation treated with silver, osmic acid, and picro- 

 carmine. 



Fig. 13. — From the same prep;iration as Figs. 9 and 10 ; .shows the end of the 

 second stage of retrogression of the fat-cell, u, a. Fat-cells in a further advanced 

 stage of exodus than those in Figs. 10 and 12. b. Cell in the last stage of granular 

 exodus, nucleus and cell-outline again becoming distinct, d, d. Group of cells in 

 a branched condition, and still containing a few granules. They appear to be 

 the wandering c( lis, resulting from original fat-cells, lying in the same position 

 as the group c. f. Spiudle-sliaped cells, resulting from the break-up of capillaries 

 that were distributed to the now absorbed fat-tract, q. Large blood-vessel, now 

 contracted and about to break up into spindle-cells, h. Nuclei of suiface 

 endothelium. 



FiG. 14. — From the same animal as Fig. 12 ; shows different stages in retro- 

 gression of fat-cells, where the granules have returned, consequently upon some 

 short return of nutrition, c, e. Cells in a fat-tract which have not yet undergone 

 granular break-up. c, c. Cells undergoing granular exodus. 6, h. Cells which have 

 undergone granular exodus, but to which the granules have returned, a. A cell 

 midway in condition between b and c, and which is assuming the branched or 

 wandering condition. /. Nuclei of surface endothelimn. d. Capillary of fat- 

 tract. Preparation treated with silver, osmic acid, and logwood. 



Fig. 15.— From mesentery of young rat weaned natundly by its mother about 

 a week previously, consequently upon which, although well supplied with food, it 

 had become very lean, and showed granular cells in tl.e branched or wandering 

 condition, a, a. Branched granular cells lying alongside a blood-vessel, to be 

 compared with the ordinary branched cells, b, b, commonly called connective- 

 tissue cells, but virtually wandering cells. 



Fig. 16. — From the same animal us Fig. 15, showing granular cells a, a, lying 

 amidst a group of ordinnry wandering cells b, b, in a natural hole of the broad 

 ligament of the liver, and, therefore, on its free surface, which they have 

 probably reached as seen in Fig. 15. These cells are now in the condition of 

 cell h. Fig. 1, with which v/e commenced, and in the same preparation differei\t 

 stages of the granular cells may be traced, until they end in the ordinary 

 wandering cell. 



All these drawings have been made by the camera lucida, under the same 

 power of 800 diameters, reduced afterwards one-half except Figs. 9 and 11 

 reduced to one-third. When not otherwise stated, the tissues have been fixed 

 by silver, stained by pyrogallate of iron, and mounted in glycerine. 



2 A 2 



