578 THE PHYSIOLOGY OF REPRODUCTION 



continue for an abnormally long period. Thus, Williams ^ records 

 a case of a woman with whom pregnancy extended for over eleven 

 lunar months after the- cessation of menstruation, instead of the 

 usual ten lunar months (i.e. about 280 days). In this case typical 

 labour pains were experienced at the end of the tenth month, but 

 these subsided after a short time, and were not renewed until four 

 weeks later, when they resulted in parturition. The same woman 

 became pregnant a second time, when the period of pregnancy was 

 again prolonged until the end of the eleventh month after the last 

 menstruation. The children on each occasion were abnormally large 

 and heavy at birth. Allen ^ has recently recorded a number of 

 further cases of prolonged gestation in women, the longest time 

 chronicled bemg 334 days. It is stated that inertia of the uterus 

 (due to fatty degeneration) is frequently associated with prolonged 

 gestation ; but the occurrence of the latter is no doubt often brought 

 about by other causes which are at present unknown. 



Cases of prolonged gestation have been observed also among 

 animals. Professor Ewart has informed the writer of a mare in his 

 possession in which the period of gestation was extended to twelve 

 months instead of the usual eleven. Other cases of prolonged 

 gestation in mares, and also in cows, have been recorded by Tessier ^ 

 and Franck-Albrecht-Goring,* and appear to be not uncommon. 

 No satisfactory reason has been suggested to account for such cases. 



According to Pinard ^ prolonged gestation may occur in Rodents 

 (Dipodillus siTnoni, Meriones sliawi, M. longifrons, Mus musculus, etc.), 

 as a result of suckling a large litter produced just previously to a 

 second gestation, as if the development of the young during the 

 latter were arrested ^by a relative insufficiency of nourishment. In 

 some cases the period of gestation was half as long again as the 

 normal duration. 



Kirkham** says that with white mice where more than two young 



1 Williams, loc. eit. 



2 Allen (L. M.), "Prolonged Gestation," Amer. Jour, of Obstet., vol. Iv., 1907. 

 ^ Tessier, " Eeeherclies sur la Dur6e de la Gestation, etc.," Mem. de I' Acad, des 



Sciences, Paris, 1817. 



* Franck-Albrecht-Gbring, "Die Trachtigkeitsdauer," Thierdrztliclie Oehurt- 

 shiilfe, vol. iv., 1901. 



^ Pinard, Article " Gestation," Eiohet's Dictionnaire de Physiologie, vol. vii., 

 Paris, 1905. 



' Kirkham, "The Prolonged Gestation Period in Suckling Mice," Anat. Rec, 

 vol. xi., 1916 ; "The Life of the White Mouse," Proc. Soc. Exp. Biol and Med., 

 vol. xvii , 1920. Kirkham and also Adler, writing earlier, state that the 

 mammary glands exert an inhibitory influence upon the stimuli coming from 

 the blastula or from the corpus luteum. (Adler, " Versuche mit ' Mammimum 

 Poehl' betreffend die Funktion der Briistdruse als innerlich sezernierendes 

 Organ," Munch. Med. Woeh., vol. lix., 1912.) That the gestation period in 

 suckling mice is lengthened had been previously noted by Daniel (" Gestation 

 in White Mice," Jour. E.vp. ZooL, vol. ix., 1910), while Miss King records 

 similar phenomena in white rats {Biol. Bull., vol. xxiv., 191.3). 



