426 E. T. Bell. 



resemblance. The fat passes out of the blood stream and is taken 

 up by the adjacent cells. Possibly the fat itself (in some soluble 

 form^^) acts directly upon the relatively undifferentiated connective 

 tissue cells causing them to pass into the preadipose and later into 

 the adipose condition. ^^ 



Detailed changes in the fat cell during development. 



As was said above, the preadipose cell is a branched cell, in 

 sections appearing usually bipolar and frequently spindle-shaped. 

 Its long coarse processes lie among the collagenous fibril] te (Figs. 

 6 and 9, Plate II; and Fig. 8, Plate I). It may accumulate small 

 fat droplets at this stage long before any further changes occur. 

 A 24.7 cm. foetus showed whole lobules of renal preadipose tissue 

 in which nearly every cell contains fat droplets (Fig. 7, Plate II). 

 Usually it seems that no fat is deposited in the cell until about the 

 time its transformation into a true rounded fat cell begins. In the 

 first formation of a fat lobule the deposition of fat begins in the pre- 

 adipose cells adjacent to a blood vessel and extends outwards. The 

 blood vessel is the center of the lobule. As the lobule gTows the pre- 

 adipose cells around its periphery are gradually converted into fat 

 cells. Some fat cells are formed inside the lobule. Most of the 

 drawings of individual fat cells were made from cells on the periphery 

 of the lobule, since the cells are not crowded there and can be more 

 easily studied. 



Text Fig. 7 shows some early stages in the formation of the fat 

 cells. The cells were drawn from the edge of a renal fat lobule of 

 a 42cm. foetus. Cell A shows the first appearance of Altmann gran- 

 ules (g), but has not yet developed a cell membrane or fat droplets. 

 It is spindle-shaped and has long processes. Cell B is not all included 

 in the section. It has fat droplets and Altmann granules. A thin 

 cell membrane (m) is present. In cell C a number of fat dro])lets 



"The physiologists have shown that fat is moved through the tissues in 

 some soluble form and not as small droplets. 



"This assumption does not, however, explain why the fat passes out of 

 the vessels at any particular place. 



