BIRDS' EGGS 



259 



muscular action of the lower part of the oviduct. But it is 

 instructive to consider these events more precisely. 



The liberation of an ovum from the ovary is due to the 

 rupturing of the follicle, and that is probably due to the 

 increased internal pressure 

 incident on the continued 

 accumulation of yolk in 

 the egg. 



It is normal for the 

 funnel-shaped end of the 

 oviduct to be pressed 

 against the ovary, so that 

 it embraces the ripe follicle 

 and receives the liberated 

 ovum. But it has been 

 proved by Raymond Pearl 

 and Maynie R. Curtis 

 (1914) that the pressure 

 from the funnel is not 

 necessary for ovulation. 



The same investigators 

 point out that various 

 things may happen when 

 ova are not caught by the 

 funnel of the oviduct but 

 go astray into the body- 

 cavity. First, they may 

 cause serious and fatal dis- 

 turbances ; second, they 

 may be absorbed rapidly 

 from the general peri- 

 toneal surface ; or third, 

 they may be walled off by the peritoneum and then absorbed. 

 If the first of these things happens, it means that the bird is 

 not in a very vigorous condition, for absorption is usually 

 facile, and it does not seem to be unprofitable. 



The abdominal viscera are so disposed that they form a 

 sort of pocket in which the ovary lies, and Maynie R. Curtis 



R.R.OVD 



OP.UR 



OROVD 

 CL 



Fig. 41 . — Female reproductive organs of 

 a hen. From a specimen, ov., the 

 ovary ; k., the kidneys ; f.t., funnel 

 that grips the egg ; ovd., oviduct ; 

 M.ovD., muscular part of oviduct ; 

 OP .OVD,, opening of oviduct ; ur., 

 ureters from the kidneys ; op.ur., 

 opening of right ureter ; r.r.ovd., rudi- 

 mentary right oviduct ; CL., cloaca. 



