130 THE PHYSIOLOGY OF REPRODUCTION 



of coition in rabbits which have given birth to young just previously, 

 and Iwanoff, 1 in confirmation of this statement, records experiments 

 in which pregnancy was induced in rabbits by the artificial injection 

 of seminal fluid shortly after parturition (cf. p. 102). 



In the mouse, 2 the rat, 3 and the guinea-pig, 4 ovulation occurs 

 spontaneously during " heat," and generally, if not invariably, during 

 O3strus. 5 



In the dog ovulation takes place independently of coition after 

 external bleeding has been going on for some days, or when it is 

 almost or quite over ; in other words, it occurs during oestrus and 

 not during the prooestrum, or at any rate not during the early stages 

 of the prooestrum. It is probable that the sow also ovulates during 

 oestrus and not during the prooestrum, since it is stated that sows are 

 most successfully served on the second or third day of "heat." 7 

 Coition, if it occurs earlier, is frequently not followed by conception. 8 

 From Hausmann's description it would seem that ovulation does 

 not take place prior to coition, but this conclusion is certainly 

 incorrect. 9 



In the ferret ovulation occurs during oestrus, but postponement 

 of coition may bring about the degeneration of the ripe follicles, 

 since they do not usually discharge spontaneously. 10 



Robinson, 11 who has made a very close study of the phenomenon of 

 maturation and ovulation in the ferret, states that the time intervening 

 between insemination and follicular rupture may vary from 3(H hours 

 to 93A hours. 



1 Iwanotf, " La Fonction des Vesicles seminales et de la Glande prostatique," 

 Jour, de Phys. et de Path. Gen., vol. ii., 1900. 



2 Sobotta, loc. cit. See also Kirkham, " Ovulation in Mammals, etc.," Biol. 

 Evil., vol. xviii., 1910. 



3 Tafani, " La Fecondation et la Segmentation studiees dans les CEufs des 

 Eattes," Arch. Ital. de Biol., vol. ii., 1889. Cf. Kirkham, loc. cit. 



4 Rubaschkin, loc. cit. See also Loeb (L.), "The Cyclic Changes in the Ovary 

 of the Guinea-pig," Jour, of Alorph., vol. xxii., 1911. 



5 According to Smith (H. P.) the ovarian cycle in mice varies from sixteen to 

 nineteen days (Proc. Amer. Assoc. A hat. (No. 55), Anat. Record, vol. xi., 1917). 

 According to Long and Quisno, rats ovulate every ten days (Science, vol. xliv., 

 1916). 



6 Marshall and Jolly, "Contributions to the Physiology of Mammalian 

 Reproduction : Part I. The (Estrous Cycle in the Dog," Phil. Trans., B., 

 vol. cxcviii., 1905. 



7 See Mackenzie and Marshall, "On Ovariotomy in Sows," Jour, of Agric. 

 Science, vol. iv., 1912. According to Corner and Ausbaugh, ovulation may 

 occur before the third day of heat, Anat. Record, vol. xii., 1917. 



8 Wallace (R.), Farm Live Stock of Great Britain, 4th Edition, London, 1907. 



9 Hausmann, Ueber die Zeugung und Entstehung des wahren weiblichen Eies, 

 etc., Hanover, 1840. 



10 Marshall, " The CEstrous Cycle in the Common Ferret," Quar. Jour. Micr. 

 Science, vol. xlviii., 1904. 



11 Robinson, "The Formation, Rupture, and Closure of Ovarian Follicles 

 in Ferrets, etc.," Trans. Roy. Hoc. Edin., vol. lii., 1918. 



