66 THE EGGS OF MAMMALS 



In a few cases, in some of the above media, and especially 

 inthis:NaClmilimol 130 - KCl 2.65 - CaCU 174 - MgCls 

 1.18 - NaHCOa 8.6 - at pH 7.2 - drops III = blood- 

 serum drops II, one or two mitoses were obtained. The addi- 

 tion of small quantities of embryonic extract, of rat foUic- 

 uline, of extract of the anterior lobe of the hypophysis to 

 the medium (either solid or liquid, natural or artificial) 

 has not noticeably modified the culture results. 



Squier (1932) using a less extensive variety of media was 

 similarly unsuccessful with guinea pig ova (see also Lewis, 

 1931). 



The limitations of the ordinary methods of tissue culture 

 are discussed further in Chapter IX in connection with the 

 investigation of the normal physiological environment of 

 developing ova. 



Nicholas and Rudnick (1933) have cultivated rat embryos 

 upon the chorioallantois of the chick, but ovum development 

 has not been studied. The embryos survive and differenti- 

 ate over a considerable period of time in the foreign environ- 

 ment. 



Cinematography of developing ova has been undertaken 

 in a number of recent investigations. Standard motion 

 picture cameras adapted for microphotography are employed. 



For a study of the comparative behavior of ova in vivo 

 and in vitro the writer has transplanted cultured ova into the 

 fallopian tubes of rabbit does (see Pincus and Enzmann, 

 1934). The operative technique requires the use of a light 

 anaesthesia, e.g., either ether preceded by atropine sulphate 

 injection to inhibit excessive mucous secretion or simple 

 urethane anaesthesia. The exposure of both tubes and 

 ovaries is had by a simple laparotomy. The ova are held 

 in a special pipette with an opening in the tube above 

 the capillary. This type of pipette permits one to take up 

 a minimum amount of fluid with the eggs, and also prevents 

 the ova from being drawn into the wide-bored portion of 

 the pipette. The capillary portion is inserted into the upper 

 3^ of the tubes and the ova expelled by gentle pressure 



