90 CARNEGIE INSTITUTION OF WASHINGTON. 



the tenth month. In a previous monograph on the causes underlying 

 the origin of human monsters, Dr. Mall calculates that there are 80 

 full-term births to every 20 abortions, and that the birth of monsters 

 is noted at about the rate of 30 to every 5,000 pregnancies. Among 

 the 1,000 cases under consideration there were 5 monsters. It follows, 

 therefore, that 25 should occur in 4,000 additional full-term births. 

 This, together with the incidence of locahzed anomalies (7.5 per cent) 

 makes it apparent that anomahes in aborted embryos occur with about 

 12 times the frequency of full-term monsters. The conclusion seems 

 to be justified that pathological embryos, as well as those normal in 

 form, are frequently associated with localized anomalies, and that 

 the terminating abortion usually is the result of lesions of the chorion 

 and its environment. Should these be slight and the uterine inflamma- 

 tion be overcome, pregnancy in all probabiUty would go on to term, 

 ending in the birth of a monster or malformed infant. Furthermore, 

 it is probable that monsters are not germinal or hereditary, but are 

 the result of external influences acting upon the ova. 



The other paper referred to is a study on the age of human embryos, 

 which was in press at the time of Dr. Mall's death and has since 

 appeared. This supplements his chapter on the same subject in the 

 Manual of Human Embryology (Keibel and Mall, 1910). In the 

 latter he gives a curve of growth, constructed upon measurements, 

 menstrual age, and date of abortion, for 1,000 specimens from the 

 various months of pregnancy, and from this he computes the mean 

 menstrual age. To the curve he adds the copulation age wherever 

 known, and this was found to fall into position 10 days after the mean 

 menstrual age. 



As pointed out by Bryce and Teacher, and now generally accepted, 

 it is probable that the menstrual cycle in man is homologous with 

 the oestrus cycle in lower mammals. Menstruation corresponds to 

 the prooestrum, and apparently a vestige of oestrus still persists, since 

 conception is of more frequent occurrence at that time. This view 

 is confirmed by the records of the Carnegie Laboratory. Dr. Mall 

 tabulates a series of 25 such cases in which the menstrual and copula- 

 tion ages are given, and adds several others from the literature. Only 

 6 of these, however, each representing the product of a single copu- 

 lation, are regarded as absolutely reliable. In these the records fall 

 almost exactly upon the above-mentioned curve. 



The time of o\^lation is still open to question, as very young human 

 ova accompanied by ovaries are extremely difficult to obtain. In 

 the Carnegie Collection there is but one such specimen, the ovum 

 measuring 5 by 3 nmi. In this the corpus luteum is well-formed, 

 sohd, and contains no blood. In Herzog's specimen, 2.3 by 1.2 nmi., 

 the corpus luteum is described as "fresh but closed." Fraenkel asserts 

 that ovulation takes place about the nineteenth day after the cessation 



