BIOLOGY OF EGGS AND IMPLANTATION 



819 



tained by measuring the Oo uptake of ferti- 

 lized rabbit ova placed in the Cartesian 

 diver and subjected to a variety of metabo- 

 lites and inhibitors can be seen in Tables 

 14.2 and 14.3 (Fridhandler, Hafez and Pin- 

 cus, 1957). In the rabbit egg, as in other 

 cells, cyanide has a markedly inhibiting ef- 

 fect on respiration. This inhibition is re- 

 versible and presumably cyanide acts 

 through the cytochrome oxidase system. Of 

 significance is the finding that glucose is not 

 an obligatory substrate for respiratory ac- 

 tivity of the fertilized rabbit egg. 



If glucose is added to the medium con- 

 taining 2- to 8-cell eggs, there is little ca- 

 pacity to carry out glycolysis. However, 

 such capacity develops during the late mor- 

 ula and blastocyst stages. This change may 

 indicate either an alteration in the mem- 

 brane characteristics of the egg, or the de- 

 velojmient of a new enzyme system as the 

 egg develops. 



The electrical characteristics of eggs and 

 their changes during activation and fertili- 

 zation have been studied in frogs, echino- 

 derms, and fish (Maeno, 1959; Ito and 

 Maeno, 1960). The electrical properties and 

 membrane characteristics of mammalian 

 eggs are entirely unknown. The use of the 

 ultramicro-electrode which has been so help- 

 ful in nerve and muscle electrophysiology 

 offers an unusual research tool for examin- 

 ing the primary process of activation of 



G. TRANSPORT OF TUB.\L OVA 



The mammalian oviducts must perform a 

 variety of functions in the transport and de- 

 velopment of the gametes (also see "Sperm 

 transport in the female genital tract") . They 

 must provide some means for transporting 

 the ovulated ova from the ovary or perio- 

 varial space into the infundibulum. Se- 

 cretions must be elaborated within the 

 infundibulum in order to provide an en- 

 vironment favorable for sperm penetration. 

 In some animals, such as the rabbit, opos- 

 sum, horse, and dog, specialized cells se- 

 crete materials which form tertiary mem- 

 branes for the eggs. Still other cells secrete 

 nutritional and possibly other substances 

 which may be essential for the normal 

 growth and development of the fertilized 

 eggs. Furthermore, the peristaltic and anti- 



peristaltic activities of the oviducts must 

 be regulated in such a way that the ova are 

 propelled forward at a definite rate and in 

 proper rotational sequence so as to be evenly 

 coated with the tertiary membranes. The 

 oviducts are indeed highly specialized or- 

 gans whose anatomic differences in the vari- 

 ous regions have been described by many 

 investigators but whose specific physiologic 

 functions still present many unsolved prob- 

 lems. 



As evidence accumulates, a happier mid- 

 dle ground of opinion is forming as to the 

 roles of the musculature and ciliary activity 

 in the downward propulsion of the eggs and 

 in the ascent of the spermatozoa. Compre- 

 hensive summaries of observations and the- 

 ories dealing with these particular problems 

 may be found in the papers and monographs 

 of Westman (1926), Parker (1931), Hart- 

 man (1939), Alden (1942b), Kneer and 

 Cless (1951). 



The more extensive investigations of the 

 oviducts during the estrous cycle include: 

 (1) The observations of Snyder (1923, 

 1924), Andersen (1927a, b), Anopolsky 

 (1928), Westman (1932), and Stange 

 (1952), on the lymphatics, the size of mus- 

 cle fibers, and the cyclic changes in the epi- 

 thelium of the Fallopian tubes of the rab- 

 bit, sow, and man. (2) The alterations of 

 rhythmic contractions in the oviducts of the 

 rat (Alden, 1942b; Odor, 1948), the sow 

 (Seckinger, 1923, 1924), the rabbit (West- 

 man, 1926), the rhesus monkey (Seckinger 

 and Corner, 1923; Westman, 1929), and 

 man (Seckinger and Snyder, 1924, 1926; 

 Westman, 1952). 



The specific method whereby the newly 

 ovulated egg is moved from the site of rup- 

 ture of the ovarian follicle to the infundibu- 

 lum is poorly understood. There is consid- 

 erable species variation in the relationship 

 of the fimbriated end of the oviduct to the 

 ovary proper. In the Muridae and Musteli- 

 dae the ovaries are almost enclosed by the 

 thin, membranous periovarial sac (Alden, 

 1942a; Wimsatt and Waldo, 1945). The 

 medusa-like infundibulum is enclosed within 

 the sac but occupies a relatively small area 

 of the periovarial space. It is believed thai 

 in those animals in which fluids accumulate 

 within the ovarian bursa at the time of ovu- 

 lation the ova are directed to the ostium by 



