l62 MAINE AGRICULTURAL EXPERIMENT STATION. I913. 



(c) the isthmus (;d) the uterus or "shell gland" and (e) the 

 vagina. These parts are shown in Figure 65. 



Each of these parts is generally supposed to play a particular 

 and exclusive role in the formation of tlie protective and nutri- 

 tive envelopes which stuTound the yolk in the complete egg as 

 laid. Thus the funnel grasps the ovule at the time of ovulation ; 

 the glands of the albumen region secrete the different sorts of 

 albumen (thick and thin) found in the egg; the shell mem- 

 branes are secreted in the isthmus; and finally the glands of 

 the uterine wall secrete the calcareous shell. This is in brief, 

 the classical picture of the physiology of the oviduct. 



For so'me 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. It is the purpose here 

 to present a certain part of the results which have been ob- 

 tained regarding tlie physiology of two of the lower 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 the existing literature indicates, 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 membrane; 

 and when it leaves the uterus all its shell. On this prevailing 

 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. The entire truthfulness 

 of this assumption was first made doubtful by the obser\^ation, 

 frequently made in connection with routine autopsy work, that 

 (a) eggs in the isthmus with completely formed shell mem- 

 branes, and (b) 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 Ply- 

 mouth Rock eggs. This observation led to an inquiry as to 



