64 THE EGGS OF IMAMMALS 



possibilities, not only for the recovery of human ova, but 

 also for checking the patency of tubes at operation. 



''The tubes which could be removed were washed by direct 

 injection through either the uterine or the fibriated ends 

 after first trimming the tube carefully along the attachment 

 of the mesosalpinx. The trimming seemed advisable, for 

 otherwise when the tube was distended with injected fluid 

 it would often kink badly. 



''A search for human tubal ova is sometimes complicated 

 by the follicle cells of the cumulus still surrounding the 

 specimens which make difficult clear observation and certain 

 identification. Although while fresh such specimens are 

 fairly transparent, it is often difficult to observe or measure 

 them accurately. Since it is probable that ova may remain 

 in the tubes for three or more days, degenerative changes 

 may be expected in a certain number of unfertilized tubal 

 ova. Also small masses or balls of cells are often encountered 

 in the tubes. These may originate in the peritoneal ca\'it.y, 

 be pinched ofT from the fimbria of the tube, or (in cases 

 where injected fluid is forced back through the tubes from 

 the uterine cavity) derived from cast-off endometrium. 

 Sometimes such cell balls contain structures which before 

 sectioning can easily be mistaken for ova. For this reason 

 unless an ovum is free from follicle cells or the cells of cumulus 

 are partly dispersed, it w^ould seem necessary that it be 

 sectioned before certain identification is possible. Further 

 check should also be made by histologic study of the most 

 recent corpus luteum." 



In obtaining both unfertilized and fertihzed ova for cul- 

 ture in litro the use of a warm washing solution is preferable. 

 This is often practically difficult and rabbit ova at least are 

 not materially affected by handling at room temperature 

 over a period of several hours. 



The usual methods of tissue culture have been employed 

 in the cultivation of mammalian ova. These include the 

 hanging drop with the ovum held in a plasma clot on a 

 coverslip over a fluid-free cavity; a plasma clot occupying 



