14 MAINE AGRICULTURAL EXPERIMENT STATION, 



Rally the glands of the uterine wall secrete the calcareous shell. 

 This is in brief, the classical picture of the physiology of the 

 oviduct. 



For some years past experiments and observations have been 

 systematically carried on in the Biological Laboratory of the 

 Maine Station with the object of acquiring a more extended 

 and precise knowledge of the physiology of the hen's oviduct 

 than is to be gained from the literature. 



Putting all the evidence together, the following account of 

 the processes by which the hen's egg acquires its white and 

 shell summarizes the results of this study. 



1. After entering the funnel the yolk remains in the so- 

 called albumen portion of the egg tube about three hours and 

 in this time acquires only about 40-50 per cent by weight of its 

 total "white", and not all of it as has hitherto been supposed. 



2. During its sojourn in the funnel and albumen portions of 

 the duct the egg acquires its chalazae and chalaziferous layer, 

 and the "thick" albumen layer. 



3. Upon entering the isthmus, in passing through which por- 

 tion of the duct something under an hour's time is occupied 

 instead of three hours as has been previously maintained, the 

 egg receives its shell membrane by a process of discrete depo- 

 sition. 



4. At the same time, and during the sojourn of the egg in 

 the uterus or shellgland it receives its outer layer of fluid, or 

 "thin" albumen which is by weight 50-60 per cent of the total 

 "white." 



5. This "thin" albumen is taken in as a dilute fluid by os- 

 mosis through the shell membranes already formed. The fluid 

 albumen added in this way diffuses into the dense albumen 

 already present, dissolves some of the latter and so brings about 

 its dilution in some degree. At the same time the fluid albu- 

 men is made more dense in this process of diffusion, and comes 

 to have the consistency of the thin layer of the normal laid 

 egg. The fluid albumen taken into the egg by osmosis is a defi- 

 nite secretion of glands of the isthmus and uterus. 



6. The addition of albumen to the egg is completed only 

 after it has been in the uterus from 5 to 7 hours. 



7. Before the acquisition of albumen by the egg is completed 

 a fairly considerable amount of shell substance has been de- 

 posited on the shell membrane. 



