400 FRANKLIN P. MALL 



and Hasler, who collected about 500 cases in which the date of 

 fruitful copulation was given. Therefore, in a group of 1200 

 cases the duration of pregnancy, when reckoned from the last 

 menstrual period, was fully ten days longer than when computed 

 from the time of copulation; and it seems to me that in order to 

 determine the true age it is necessary to deduct these ten days 

 from the menstrual age. Even then I believe we should be care- 

 ful not to use the word true, since the time of copulation does 

 not necessarily record the time of fertilization. For this reason 

 it might be well if we introduced the term, copulation age, 

 to distinguish it from menstrual age, and from two other ages 

 I am about to give. These could be termed ovulation age and 

 fertilization age, the latter being the only true age, since we 

 must always figure the beginning of development from the time 

 of fertilization. 



The curve in the chart, which I gave in my publication, as 

 representing the true age, but which I now will speak of as the 

 copulation age, was constructed from cases of newborn children, 

 and is probably the more . valuable because it eliminates all of 

 the irregularities of early pregnancy which accompany natural 

 abortion. After the curve was completed, however, we received 

 into our collection a few embryos, measuring less than 25 mm., the 

 accompanying records of which gave the time of copulation as 

 well as of menstruation. The copulation ages of these specimens 

 were then entered upon the chart shown in the IVIanual with 

 stars (fig. 147), and curiously enough nearly all of them fall 

 exactly upon the line of the curve, showing that what was as- 

 sumed to be a difference at the end of pregnancy is also indicated 

 again in specimens from the beginning of pregnancy. In both 

 cases the difference between the menstrual age and the copula- 

 tion age is about 10 days. When this chart was made it con- 

 tained seven stars, but after it had been sent to the printer I 

 found another case in the literature. Also, about the same time 

 I received a copj^ of a book published by Bryce and Teacher,^ 

 which gave a second case, and these were added to the curve. 



^ Bryce and Teacher 1908 Contributions to the study of the early devcktp- 

 ment and imbedding of the human ovum. Glasgow. 



