AUTHOR S ABSTRACT OF THIS PAPER ISSDED BY 

 THE BIBLIOGRAPHIC SERVICE, DECEMBER 29 



ON THE AGE OF HUMAN EMBRYOS 



FRANKLIN P. MALL 



Johns Hopkins Medical School, Baltimore, Md. 



TWO FIGURES AND EIGHT TABLES 



In the Manual of Human Embryology, published seven years 

 ago, I presented the evidence by which we may determine the 

 age of an embryo or fetus, in my chapter dealing with this sub- 

 ject. ^ It was there pointed out that the best che«k in arranging 

 embryos in time sequence is obtained from our knowledge of 

 comparative embryology; also, that the only factor which can 

 be depended upon in every case is what I then termed the 

 'menstrual age;' that is, the age of the embryo as computed by 

 the time elapsing between the beginning of the last menstrual 

 period and the date of the abortion. 



In order to procure a satisfactory curve of growth for the 

 whole period of gestation, I succeeded in collecting about 1000 

 specimens from the different months of pregnancy with the 

 data given concerning them; namely, the measurements of the 

 embryos and the dates of menstruation and of abortion. It was 

 also necessary to establish standard measurements for the 

 embryos, chief of which are sitting-height and standing-height; 



1 Mall, Franklin P. 1910 Determination of the age of human embryos and 

 fetuses. Manual of Human Embryology, Chap. 8. Edited by Franz Keibel and 

 Franklin P. Mall, Philadelphia; German edition, Leipzig, 1910. 



1903 See also Note on the collection of human embryos in the Anatomical 

 Laboratory of the Johns Hopkins University. Johns Hopkins Hospital Bulletin, 

 vol. 14. 



In the second paper I gave a formula by which the age of embryos up to 100 

 mm. long could be determined. That is, to multiply the CR length in millimeters 

 by 100 and extract the square root ; the product is the age in days. I wish to state 

 that this formula gives the age according to the His convention, which I now 

 believe to be incorrect, as demonstrated in my chapter in the Manual. This con- 

 clusion was also reached independently by Bryce and Teacher. 



A fairly complete bibliography is to be found in the papers b}^ Mall (1), Bryce 

 and Teacher (3), Triepel (2) and Grosser (6). 



397 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 2 



