PHYSIOLOGY OF THE OVIDUCT . 119 
cent at the upper end of the isthmus, the relative amount of this 
element in the albumen diminishes steadily till the egg is laid. 
The point of greatest interest and importance in connection 
with these chemical data, hinges upon the absolute amount of 
nitrogen in the albumen. Since it is solely the thin albumen 
layer which is added after the egg leaves the albumen portion of 
the oviduct the possibility is at once suggested that what happens 
in the lower portions of the duct is not a true secretion of another 
albumen layer but merely a taking up of water from the blood 
by osmosis, and a dilution or partial solution of the dense albumen 
already present. Such a view assumes in other words that all 
that is added to the albumen after the egg enters the isthmus is 
water. 
Clearly the only way to test finally the validity of this idea is to 
earry out such chemical determinations as are tabled above. 
The last column of table 2 shows the available evidence, which 
appears reasonably clear in its significance, though because of 
the minute absolute amount of nitrogen in the white of an egg 
the case is not a simple one. What the figures from the analyses 
of thirteen oviduct eggs show is that with four exceptions, the 
oviduct egg has absolutely less nitrogen in its albumen than the 
normal laid egg of the same hen. This, of course, is what would 
be expected if there is an actual secretion of albumen by the glands 
of the oviduct, and this secretion is added to the egg. It means 
that these oviduct eggs have been removed before they received 
their full amount of albumen. If it were the case, on the contrary, 
that only water was added to the egg after it left the albumen 
portion of the duct, it would be expected that the amount of 
nitrogen would be the same in an oviduct egg from the isthmus or 
uterus as in the normal laid egg. The chemical data clearly indicate 
that there is a definite addition of albumen to the egg vn the isthmus 
and shell gland, and that the thin albumen layer does not represent 
solely a dilution of the-dense layer. 
The four cases in which the analyses furnish an exception to this 
rule are undoubtedly to be explained as the result of fluctuation 
in the absolute size of the egg. It will be noted that each of these 
four eggs have been in the uterus some time and would therefore 
