PHYSIOLOGY OF THE OVIDUCT 101 
For some years past experiments and observations have been 
systematically carried on in this laboratory with the object of 
acquiring a more extended and precise knowledge of the physi- 
ology of the hen’s oviduct than is to be gained from the literature. 
It is the purpose of this paper to present a certain part of the 
results obtained bearing upon the physiology of two of the lower 
(caudal) morphological divisions of the duct, namely, the isthmus 
and the uterus. Our results indicate that these portions of the 
oviduct perform certain functions which have not hitherto been 
observed or described. 
So far as we are able to learn from the existing literature the 
opinion has been held by all who have worked upon the subject 
that the particular functional activity of each portion of the 
oviduct (as above described) is limited to that portion. Thus 
it is commonly held that when an egg in its passage down the 
oviduct leaves the albumen portion it has all the albumen it will 
ever have; when it leaves the isthmus it has all its shell mem- 
branes; and when it leaves the uterus all its shell. On this pre- 
vailing view there are in the albumen portion only albumen 
secreting glands; in the isthmus only membrane secreting glands; 
and in the uterus only shell secreting glands. We were first led 
to doubt the entire adequacy of this assumption by the observa- 
tion, frequently made in connection with routine autopsy work, 
that eggs in the isthmus with completely formed shell membranes, 
and eggs in the uterus bearing in addition to the complete shell 
membranes a partially formed shell, weighed considerably less 
than the normal average for laid Barred Plymouth Rock eggs. 
This observation led to an inquiry as to whether (a) this apparent 
lower weight of presumably completed, but not laid eggs, as 
compared with those which had been laid, was a real phenomenon 
of general occurrence, and (b) if so, to what it was due. Does 
the egg increase in weight after the formation of shell membranes 
and shell merely by the absorption of water, or by the actual 
addition of new albumen? These are the problems with which 
the present paper has to do. 
We may now turn to the consideration of the observational 
and experimental data. 
