A Further Note on the Nutrition of the Early Embryo. 333 
the other hand, were profuse and extremely mucoid. The above secretions, 
both uterine, cervical, and vaginal, were slightly alkaline to litmus. 
A series of experiments was made upon the egg-white surrounding the 
developing chick. It is well known how this substance decreases in bulk as 
development proceeds, but apparently no means have been taken to show 
what changes are undergone during this process. In egg-white one has to 
deal with three main distinct components—the proteid, the water, and the 
salts. Milroy states that normal egg-white contains 10 to 13 per cent. of 
proteid (2.¢., approximately 87 to 90 per cent. of water), but his results were 
obtained after straining through muslin, which naturally would lead to 
a higher percentage of water when compared with results obtained where no 
straining was introduced. 
As incubation proceeds, the most obvious change in the egg-white, after 
its diminution in bulk, is its extreme tenacity, so much so that it is with 
great difficulty that it can be removed for examination. It also becomes 
more yellowish-green in colour, probably due to its more concentrated state. 
It is evident, therefore, that the loss of water has been disproportionate to 
the loss of proteid. That this is so is demonstrated by the percentages of 
water taken at different stages, when it will be seen that the disproportion 
increases as incubation proceeds (vide Diagram). 
The most remarkable change is that which affects the reactions of the 
substance : instead of being soluble in distilled water, as is fresh egg-white, 
a white coagulum is formed at the interface between the water and the 
proteid, rendering solution difficult ; if, however, the substance is shaken up 
with distilled water in a flask over a period of some days, with a few drops of 
xylol added in order to ensure sterility, it will be found that on each day 
a certain portion of the substance will have become soluble, leaving a 
gelatinous mass in which, on section, foetal villi can be demonstrated. In 
the early stages it is somewhat soluble in normal saline solution, but later it 
becomes more and more difficult to dissolve. On heating, the substance 
becomes dried, but fails to coagulate. It is precipitated by dialysis. At 
this point certain changes are going on in the salts of the egg-white, as 
demonstrated by the amount of ash after incineration. It will be seen 
(vide Diagram) that while in relation to the amount of egg-white the 
percentage of water is rapidly decreasing, that of the salts remains much the 
same for unfertilised as for fertilised eggs (whether due to osmotic influence 
or not is conjecturable). But it is evident that as the egg-white loses its 
water the proteid becomes more and more concentrated, so that, taken 
in relation to the amount of proteid (dried at 110°), that of the salts shows 
a more or less corresponding decrease, which is interesting from a com- 
