10 



RAYMOND PEARL AND ALICE M. BORING 



The last formed corpus luteum is of a salmon pink color, 

 due to a combination of the blood color and the lutein color. 

 Sections show it composed of large plump cells with rounded 

 nuclei, as described by Corner. These luteum cells are scat- 

 tered in the midst of an areolar connective tissue groundwork 

 (fig. 18 and fig. E). In dehydrating for embedding, the abso- 

 lute alcohol and xylol become very yellow, indicating that the 

 cells contain something soluble in these reagents. This is of 

 course one chemical character of lutein. 



Fig. E Cells from youngest corpus luteum of cow. (X 950.) Compare 

 figure 18. 



Fig. F Cells from older corpus luteum of cow, showing pigment developed 

 in cells. (X 950.) Compare figure 19 and figure 21. 



The next to last corpus luteum is much reduced in size. Its 

 color has lost the pinkish shade and it appears a solid bright 

 yellow. This is also soluble in absolute alcohol and xylol as 

 in the first stage. The cells and nuclei both look a little shrunken. 

 In one cow, this second corpus luteum contained a few amor- 

 phous yellow particles like those described foi the hen. 



