44:6 GENERATION. 



Duration of Pregnancy.- The duration of pregnancy, 

 dating from a fruitful intercourse, must be considered as va- 

 riable, within certain limits. The method of calculation 

 most in use by obstetricians is, to date from the end of the 

 last menstrual period. Dr. Matthews Duncan, who has made 

 quite a number of observations upon this point, states that 

 the 278th day after the end of the last menses is the average 

 day of delivery ; but he admits that his method of calculation 

 is rough, though he cannot find any that is more reliable. 

 The observations upon which this opinion is based are the 

 following : The day was predicted in 153 cases ; in 10 cases, 

 confinement occurred on the exact day ; in 80 cases, the con- 

 finement occurred sooner, presenting an average of 7 days for 

 each case ; and, in 63 cases, the confinement occurred later, 

 presenting an average of 8 days for each case. 1 The great 

 difficulty in predicting the exact time of confinement, which is 

 very important in practice, is mainly due to the comparatively 

 small number of reliable observations in which the pregnancy 

 can be dated from a single intercourse, or intercourse occur- 

 ring within two or three days. We have received from Prof. 

 Fordyce Barker the following very interesting account of a 

 case in which this observation was made, in his own practice : 

 A lady concerning whom there could be no suspicion of in- 

 accuracy, residing in New York, received a visit from her 

 husband, after a long interval of absence. He arrived in 

 this city from New Orleans, remained thirty-six hours, and 

 then went to Europe, where he remained for four months. 

 Exactly 298 days from the date of the first visit of the hus- 

 band, the lady was confined and delivered by Prof. Barker. 

 This occurred in 1852. 2 Taking into account the various 

 cases which are quoted by authors, in which conception has 

 been supposed to follow a single coitus, there appears to be a 

 range of variation in the duration of pregnancy, according 



1 J. MATTHEWS DUNCAN, Fecundity, Fertility, Sterility and Allied Topics, 

 New York, 1871, p. 449. 



2 Communication from Prof. Barker. 



