LIVER CELLS FROM CHICK EMBRYO 291 



When trypan blue was added to the medium at the time of 

 planting, deep blue granules were seen in all the cells from the 

 time of their first appearance. As trypan blue enters the cells 

 very slowly, it cannot be successfully used supra-vitally and stain- 

 ing of the granules by it cannot be watched as in the case of 

 neutral red. It is therefore difficult, perhaps impossible, to be 

 sure always that the trypan blue granules are pre-existing granules 

 to which the dye has become attached. We believe, however, 

 that the trypan blue, like the neutral red, is deposited only in 

 pre-existing granules. The granules stained by trypan blue 

 resembled the neutral red granules in every way. When explants 

 from the same embryo were cultivated in the same medium, 

 except that one lot contained trypan blue and the other lot 

 neutral red, the blue and the red granules were alike in shape, 

 distribution and behavior. In size and number there was often 

 some difference; the trypan blue cultures were usually 18 to 24 

 hours ahead of unstained or neutral red cultures in rate of growth, , 

 and showed more and larger granules than the neutral red cultures 

 of the same age. 



When explants were cultivated in media containing both 

 neutral red and trypan blue, there appeared in the cells granules 

 varying in color from a rose-red to a purple, depending on the 

 relative amounts of the two dyes present. These granules had 

 the same characteristics of shape, size, distribution and behavior 

 as the yellow-red granules of the neutral-red cultures and the 

 blue granules of the trypan-blue cultures. Three sets of cultures 

 from the same embryo were made at the same time, one with 

 neutral red, one with trypan blue, and one with trypan blue and 

 neutral red in the media. The red, the blue and the lavender 

 granules of the three sets of cultures at a given age were alike 

 in every way except in number and size ; the trypan-blue granules 

 usually exceeded the others in these respects; the doubly-stained 

 ones were second, and the neutral red the smallest and fewest. 

 When a very dilute solution of neutral red was added to a trypan- 

 blue culture no yellow-red granules appeared, but the blue gran- 

 ules could be seen to change to purple, then to lavender, and, if 

 enough neutral red were present or if more were added, to g 



