WHITE AND YELLOW YOLK OF OVA 457 
port of the relation between this ‘organized’ and this ‘living’ 
material we shall know later; in the meantime, each bit of informa- 
tion is doubly welcome because it concerns the most interesting 
form of protoplasm—the egg—at what is probably its most inter- 
esting period. Perhaps, then, the substance that has seemed to 
have but blundered in where it could blind us most, may itself 
prove to be a mirror for many a secret that we have else- 
where sought in vain. 
A METHOD OF MEASURING THE RATE OF GROWTH OF RAPIDLY 
GROWING OVA 
The present studies began with an attempt to learn the cause 
of the stratified condition of the yolk of the hen’s egg. It was 
suggested to me by results of an earlier study (08) that the al- 
ternate layers of white and yellow yolk in the egg may be the 
result of the daily rhythm of nutrition—connected with high 
and low blood-pressure—which I had discovered in birds, and which 
I had shown to be the cause of the alternate fault-bars and funda- 
mental bars of birds’ feathers; it being there found that the daily 
variation in nutritive conditions in birds is sufficient to produce 
structurally perfect, and structurally imperfect parts in their 
rapidly growing feather germs. To test the suggestion, then, one 
might need only to learn the rate of growth of a bird’s egg. What 
is the rate of growth in the eggs of the common fowl? This had 
not been determined, and no way of determining it was known. 
It occurred to methat Sudan III might be used for this purpose. 
Knowing that Sudan was not destroyed in passing through 
the intestinal wall, (Daddi) that it circulated tied to the fatty acids 
of the food, and that the fatty acids of the food were laid down 
unchanged in the egg (Henriques and Hansen, ’03), I inferred that 
Sudan given with fatty food would be laid down in the egg. 
Moreover, it seemed possible by regulating the dosage and using 
proper intervals between feedings, to get laying hens to put 
this bright pigment down as definite bands in their growing ova, 
and thus enable one to determine the rate of growth. 
The first experiment was as successful as the last. When such 
Sudan-containing eggs’ were hard-boiled and sectioned under 
