DURATION OF PREGNANCY. 447 



to Leishman, of no less than 40 days, the extremes being 260 

 and 300 days. 1 



In the very interesting observations of Kundrat and En- 

 gelmann, on the changes of the uterine mucous membrane 

 during menstruation, to which we have already referred, 2 the 

 idea is advanced that pregnancy dates really from a men- 

 strual period which is prevented, as far as a discharge of 

 blood is concerned, by fecundation of an ovum, and not from 

 the period immediately preceding, in which the flow takes 

 place. 8 If we adopt this view, the changes in the mucous 

 membrane of the uterus ordinarily terminate in a fatty de- 

 generation of the vascular walls, which results in a capillary 

 haemorrhage ; if, however, an ovum be fecundated, these 

 changes do not pass into fatty degeneration, but advance to 

 an hypertrophy, which is the first stage in the formation of 

 the decidua. This view was advanced, a short time before the 

 publication of the researches of Kundrat and Engelmann, by 

 Loewenhardt, in a very elaborate clinical memoir upon the 

 duration of pregnancy. 4 The arguments in opposition to 

 this method of calculating the duration of pregnancy are the 

 following : The time, with relation to the menstrual flow, at 

 which an ovum is discharged has not been accurately deter- 

 mined ; and it is certain that ovulation frequently does not 

 take place until after the flow of blood has been established. 

 This question we have fully considered in a previous chapter. 5 

 It is probable, also, that intercourse is most liable to be fol- 

 lowed by fecundation, when it occurs just after the cessation 

 of a menstrual period, and when the female often presents 

 unusual sexual excitement ; but it is true that fecundation may 

 follow intercourse at any time. If we admit that fecundation 



1 LEISHMAN, System of Midwifery, Glasgow, 1873, p. 188. 



2 See page 306. 



3 KDNDRAT UND ENGELMANN, Untersucliungen uber die Uterusschleimhaut. 

 Medizinische Jahrbucher, Wien, 1873, S. 143. 



4 LOEWENHARDT, Die Berechnung und die Dauer der Schwangerschaft.~* 

 Archivfiir Gynaekologie, Berlin, 1872, Bd. iii., S. 456, et seq. 



6 See page 293. 



159 



