86 Walter E. Dandy. 
giving the model a total length of 32.6 em. <A shrinkage space 
between the layers of tissue aided materially in the reconstruction 
without sacrificing tissue. The model is so constructed that every 
detail may be exposed by cuts and windows. 
Upon presentation of an embryo the question naturally arises, 
is it normal? ‘The history of a mechanical abortion points very 
strongly toward a normal embryo. It compares very closely with 
the few other known embryos of this period. The tissues, including 
the chorion, are excellently preserved and show no degenerative 
changes. 
AGE. 
From the history that the menstrual period passed about two weeks, 
the age of 13-14 days would fit very nicely into the conventional 
Reichert-His theory of fertilization and age of embryos. Recent obser- 
vations however by Mall in 1000 cases with menstrual history have 
shown that we underestimate the age of young embryos, on an aver- 
age about 10 days, that fertilization is not restricted to the period 
immediately before the menstrual period, but may occur at any time 
in the intermenstrual period. Bryce and Teacher also came to the 
same conclusions and illustrate this in a well constructed diagram 
of the menstrual cycle. This obviates the remarkable distortion 
which has been necessary to harmonize age with size and progress 
of development, and makes the human embryo much less precocious 
in its development. In conformity to the above observations the 
true age of this embryo is probably about 24° days, which would 
make the time of fertilization occur about ten days before the time 
for onset of lapsed menstrual period or about eighteen days after 
beginning of the last menstrual period. 
Tur ADNEXA. 
Chorion. The chorionic membrane is about 0.1 mm. thick, and 
is covered with many branching villi varying in size up to 1.25 
mm. in length and 0.1 mm, in thickness. These villi are more 
numerous at the point of attachment of the bauchstiel and gradually 
fade away on all sides until finally a clear zone results from their 
absence on the opposite pole. 
